Ocean colonization

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Ocean_colonization

Ocean colonization is the theory of extending society territorially to the ocean by permanent settlements floating on the ocean surface and submerged below, employing offshore construction. In a broader sense the ocean being subject of colonization and colonialism has been critically identified with exploitive ocean development, such as deep sea mining. In this regard blue justice groups have also used the term blue colonization.

Ocean Colonization
The theory of developing permanent dwellings in the ocean, both floating and sunken, to allow permanent human settlement. This idea was first suggested by Friedman and Gramlich, and has been researched since the early 1990s.

The process of extending space available for humans to inhabit involves developing seasteads such as artificial islands, floating rigid structures, extreme-sized cruise ships or even submerged structures, to provide permanent living quarters for sections of the world's population. Specifically catering for the growing issue of overpopulation, and need for extra housing as a result, the urban theorists that have pursued this idea also suggesting it as a sustainable form of living to help assist climate change  Colonies may form their own sovereign state of independence, with these structures also being generally less impacted by natural disasters.

However this theory for future urban planning has been critiqued by other scientists, suggesting that developing artificial structures in an aquatic environment will disrupt the natural marine ecosystem and may instead be impacted by aquatic natural disasters such as tsunamis. The debate against this theory further notes the threat of security of these colonies and the potential lack of protection without an overseeing government or body.

The utopian theory of ocean colonisation has been explored and visually explained in many forms of entertainment such as in gaming, virtual realities and science-fiction movies, to show the potentially positive and negative changes on societies daily living.

Lessons learned from ocean colonization may prove applicable to space colonization. The ocean may prove simpler to colonize than space and thus occur first, providing a proving ground for the latter. In particular, the issue of sovereignty may bear many similarities between ocean and space colonization; adjustments to social life under harsher circumstances would apply similarly to the ocean and to space; and many technologies may have uses in both environments. 

Technologies

Underwater construction

Main article: Underwater construction

See also: Submarine pipelines

Underwater habitats are examples of underwater structures.

Submerged Structures

Submerged structures are sunken, air-tight vessels that either sit at an intermediate position or attached to the ocean floor that create an underwater metropolis for residences and businesses.

Proposed Designs

H2ome is a project for building sea floor homes, along with high-end resorts and hotels.

Ocean Spiral City is a $26 billion Japanese project, with research and designing being underway to potentially house 5000 people and may be a reality by 2030.

Offshore construction

Main articles: Offshore construction and Accommodation platform

See also: Offshore geotechnical engineering, Oil platform, Fixed platform, Offshore windfarm, Aquaculture, Maricultire, and Offshore aquaculture

Offshore construction is one of the main forms of ocean colonization.

Land Reclamation

Land reclamation, or artificial islands, are the man-made process of relocating rock or placing cement in a sea, ocean or river bed, to extend or create a new area of liveable land in the ocean. This process involves creating a solid base on the sea floor and further building upon it with materials such as clay, sand and soil to form a new island-like structure above the water surface. It therefore expands the area for potential development space, supporting the erection of buildings or other necessary urban developments in response to support human activities, by utilising this otherwise untouched space for more ‘productive’ uses. This ocean colonisation technique is the most developed in terms of planning and implementation in the present day.

Present-day Examples

Palm Jumeriah

Palm Island, Dubai

The Palm Jumeriah is the main of the three artificial islands in Dubai, United Arab Emirates, to be developed. The name ‘Palm’ resembles its palm-tree like design when viewed aerially, and is both culturally and symbolically relevant to the coastal city. This land reclamation project began in 2001 and involved the movement of 94 million cubic metres of sand and 5.5 million cubic metres of rock off-shore in the Persian Gulf, to allow the development of luxury beachfront villas for both residential and commercial purposes.

Kansai Airport located off the coast of Osaka Bay

Kansai International Airport

Kansai International Airport located in Osaka Bay, Japan was created in 1987, due to overcrowding at the nearby Osaka Airport. Developers suggested Japan's mountain terrain  is not conducive to the development of necessary flat space required for an airport and thus developed an artificial island in the bay, with a connecting bridge to support both travel and freight arrivals and departures.

Portier Cove

Portier Cove is a new eco-district extended off the coast of Monaco designed to reduce greenhouse emissions in the area. The 125m long extension project re-began in 2011 and plans to provide a hectare of space for retail, parks, offices, apartments and private villas, to support their national issue of a growing population.

Floating Structures

Artist impression of a floating residence

Very Large Floating Structures (VLFS)  or Seasteads are artificially man-made pontoons, designed to float on the surface of the ocean or sea to house permanent residents. They have a large surface area and are designed to not be bound to a certain government but instead form their own community through clusters of floating structures. This type of technology has only be theorised and is yet to be developed, however a variety of companies have investment project plans underway.

Proposed Designs

The Seasteading Institute

Seasteading refers to building buoyant, permanent structures to float on the surface of the ocean to support human settlements and colonies.

The idea constructed by Friedman and Gramlich, who founded the Seasteading Institute, is now defined in the Oxford English Dictionary. The pair received $500k funding from PayPal Peter Thiel, to begin designing and constructing their idea in 2008. 

Oceanix City

Architectural company BIG proposed their design of the Oceanix City, involving a series of inhabitable floating villages, clustered together to form an archipelago that could house 10,000 residents. The proposed design was developed in response to the effects of climate change such as rising sea levels and an increase in hurricanes in the Polynesian region, that threaten many tropical island nations from being eradicated. The design also outlines its intentions to incorporate predominantly renewable energy sources such as wind and water.

Cruise Ships

The idea of cruise ships as part of the theory of ocean colonisation, surpass the typical modern-day commercial cruise ships. This technology imagines a large scale vessel, supporting permanent residence on board that can freely move about the world's oceans and seas. These ships include residential, retail, sport, commercial and entertainment quarters on board.

Proposed Designs

The Freedom Ship

The ideal size and style is outlined in the concept of the ‘Freedom Ship’ design by US engineer Norman Nixon, proposing a 4000 ft length vessel that has the capability to house 60,000 residents and 15,000 personnel   - with an estimated cost of $10 billion (USD).

Present Day Example

'The World' Ship - the largest commercial floating vessel

The World Ship

‘The World’ ship debuted in 2015, sitting at 644 ft long and is the largest, residential cruise ship presently in the world. This vessel is the closest, existent ship to the idealised ‘Freedom Ship’ design that hopes to support permanent life on board a ship. Permanent residency on the ship costs between $3million (USD) to $15million (USD) per room.

Examples in Media

• Seaquest, a 1990s science-fiction TV series about a spacious high-tech submarine by a future global government, patrolling the oceans which have been settled.
• THE MEG, 2018 science-fiction movie, based in living in an underwater research facility.

Impacts of theory

Environmental

Climate change

Gradual rise of sea levels since 1992

It is predicted by 2100, sea levels will have risen by 1–3 meters as a result of global warming, to which by 2050 are estimated to impact 90% of the world's coastal cities. Theorists who support ocean colonization theories hope to face the issue and provide a solution for groups and nations worldwide that are most at risk.

Island in Tuvalu

For example, Polynesian island nations such as Tuvalu with a population of 10,000 are expected to be fully submerged by water in approximately 30–50 years 

Entrepreneurs who have devised these technologies to support the colonization of the seas suggest their design will have an overall minimal carbon footprint.

Plastic bottles utilized as building material

Recycled and environmentally-friendly materials such as recycled plastics and locally sourced coconut fibres will constitute a large proportion of building materials required for construction.

To minimise the use of pollutant energy output in the environment contributing to this rapid global warming, designers suggest using predominantly renewable energy from sources such as water, wind  and solar power.

Floating wind turbine power station

Designers also intend to utilize bicycles, electric and hydrogen vehicles as the primary transport system on board to prevent extra CO₂ emissions.

Ultimately, project designers, entrepreneurs and scientists are aiming to collaborate to create a structure allowing “the formation of an eco-sustainable production and consumption cycle in the future human habitat”.

The primary group impacted by the effects of climate change, the Pacific Island Nations, are the target demographic identified for the ocean colony projects to which they are still able to remain in their familiar and culturally significant island environment. In 2017, French Polynesia signed an agreement with the Seasteading Institute to utilise their land for testing of the world's first floating town.

Green Float is another example of a project hoping to develop a carbon negative city within the Equatorial Pacific Ocean, with it set to house 100,000 locals by joining multiple floating modules. They hypothesise a 40% reduction in CO₂ emissions through more environmentally friendly and energy efficient modes of transport and power. 

Areas of the world susceptible to natural disasters

Protection From Natural Disasters

The number of natural disasters occurring in the world has grown by 357 from 1919 to 2019, according to Our World in Data, with 90,000 people killed annually as a result of this extreme weather. According to this data, the main economic impacts have primarily come from extreme weather events, wildfires and flooding. Due to these economic effects, cities such as Boston, Miami and San Francisco are exploring this idea of ocean colonization as they try to protect their coastlines from an increase in flooding, rising sea levels and earthquakes respectively. Ocean colony technologies are said to be less impacted by common territorial natural disasters and even extreme aquatic weather such as damaging waves as they occupy more shallow waters. For example, the world's first floating hotel, the Barrier Reef Floating Resort, sat 70 km off the coast of Townsville, Australia and in 1988 withheld against a cyclone.

Aquatic Natural Disasters

According to theorists and scientists at the Seasteading Institute who have begun conducting research into aquatic environments as liveable spaces, many of the technologies supporting ocean colonization are set to mainly be impacted by rogue waves and storms. However, other aquatic natural disasters such as Tsunamis, Friedman says would have little impact on the structures yet only raise water levels.

Research in the 1990s emerged regarding the hydro-elasticity of rigid structures at the face of relentless and on-going wave movement  to which lead to modern scientists such as Suzuki (2006), voicing their concern of the potentially poor integrity of aquatic structures impacting by constant motion and vibration.

Breakwaters used to minimize wave destruction

Further modern research and design has also been situated around testing the computation fluid dynamics of resistance against vortex formations of water, such as cyclones that form and therefore threaten ocean environments.

Cyclone formation over ocean

Spar platforms, artificial and natural breakwaters and active repositioning, if applicable, of ocean structures to avoid storms are some suggestions and technologies suggested by ocean colonization supporters and scientists to combat extreme aquatic weather events. Entrepreneurs such as Friedman, have acknowledged and are aware of the care that must be taken in the engineering process of these designs.

Disruption to Marine Ecosystem

Biologists have identified the individualised negative impacts of the technologies that support the implementation of colonization, by their effect on the disruption to the local marine ecosystem.

According to scientists, the process of land reclamation can lead to the erosion of natural soil and land, through this human-made and unnatural movement of sediment that consequently disrupts the natural geological cycle.

Scientists at Marine Insight, have conducted studies of the environmental impacts of commercial cruise ships, with these impacts predicted to be similar to the technologies allowing ocean colonization. Currently, these vessels cause air pollution through the emission of toxic gases that increase in the acidification of the ocean.

Their research also showed the noise pollution from these ships can disturb the hearing of marine animals and mammals.

Furthermore, the leaking of chemicals, grey water and blackwater into the ocean can lead to the accumulation of harmful chemicals, increasing the water concentration, that local flora and fauna are accustomed to. These studies of cruise ships and their impact of the marine environment have been incorporated by ocean colonization scientists and designers, as they are the closest, existent technology to their proposed projects.

Social

World population growth from 1700 to 2100

 

Ocean surface coverage

Overpopulation/Housing Shortage Crisis

Ocean colonization is said by theorists to be a potential solution to the world's growing population, with 7.78 billion people currently inhabiting Earth as of May 2020. The BBC claim that 11 billion people is Earth's carrying capacity even after adjusting consumption behaviours, with the UN predicting this number to be reached by 2100. With the world's oceans covering 70% of the planet's surface, this space has been therefore seen as a viable, long-term solution to allow an expansion and extension of inhabitable space by 50%. Pioneers of this colonization theory suggest the new spaces to also cater for new and more jobs, and may be a particular solution to the moral and political dilemma of housing as well as the consequential increased number of climate refugees.

Political Economic

Sovereign Independence

Central entrepreneurs to this theory have suggested that it hosts the potential for a degree of autonomy of residences, currently operating in more strict political systems. As a result, ocean colonisation has been posed as a potential solution to poor governance, in which sovereign states may begin formation of greater personal freedoms, little state regulation and clearly defined state intentions. Despite critical theorists at the Seasteading Institute suggesting their design to allow people to “experiment with new forms of government”, however socialists critique this idea, seeing it as a possibility bypass tax laws  in international waters. Projects such as the Freedom Ship and those by the Seasteading Institute, have proposed the idea for the installation of their designs in Polynesian water however are exempt by unique governing framework permitting significant autonomy from Polynesian laws.

Countries and their exclusive economic zones

Under Article 60 of the United Nations Convention on Law of the Seas (UNCLOS), “artificial islands, installations and structures” have the right to build in exclusive economic zones to coastal nations, however these coastal nations still hold sovereignty of the 12 nautical miles adjacent to that coast.

Little has been vocalised on the development of essential services i.e. schools, hospitals etc., within these ocean colony structures yet theorists say it is likely host or closest nations will be relied upon until the initial population grows. With intentions to build beyond territorial seas in exclusive economic zones, the likelihood of the idea for pure sovereignty has been questioned by critics.

Expense

According entrepreneurs at the Seasteading Institute, their particular technology of floating modules is said to be high, with a predicted cost of  $10,000 - $100,000 per 1 acre of a seastead, comprised purely by volunteers. Similarly, Friedman, co-founder of the Seasteading Institute, has estimated the entire project to cost a few hundred million. As mentioned earlier, other projects such as the Ocean Spiral City, are set to cost $26 billion 

Critics have responded to these future plans; labelling them as “elitist, impractical and delusional”, with “the number of people accommodated limited”.

These projects will therefore rely on investors, which is acknowledged by ocean colonization theorists who state the “first people to benefit will be the privileged who can afford to invest in the project”. However skeptics criticize the idea suggesting it is ultimately designed for capitalist gain, rather than a potential solution for the future society.

Lack of Security

Without an overseeing government and lack of taxes, critics of ocean colonisation suggest there would be little security provided in the open waters, in terms of economically and regarding human rights laws. Theorists are considered by threat of being prey to pirates, with colonies on board therefore having minimal personal protection.

There has been resistance to this seemingly capital-intensive project, as critics of the idea suggest private law cannot be embraced if it challenges that of the public laws. Ocean colonization theorists have acknowledged the necessary assignment of responsibility of land and resources into private hands, to ensure that a party is liable. This assigned responsibility is suggested to rely upon existing legal frameworks regarding property, contract and commercial laws to protect colonies. Ocean colonisation theorists are currently working to balance the idea of freedom with security 

Adaptations to Living

Developing these technologies and strategies will ultimately require changes to daily living.

Hydroponic farms

Positive

Many current day activities will remain relatively unchanged and un-impacted, such as many of the ‘modern necessities’ i.e. heating, lighting, kitchen appliances, hot water systems. ‘They would require specially consideration and design, however most technologies would still be available’ says Friedman.

With such proximity to water resources, there would be a reliance on hydroponics to account for the limited space on the surface, that would generate energy and support the growth of crops. Similarly, to conserve space, vertical gardens have been suggested by designers for growing and composting.

Humans are more likely to accustom to this environment, as psychologically they are more comfortable with water, with humanity gradually moving to reside to coast and have historically always operated close to water ways.

Negative

On the other hand, humans are less likely to adapt to this possible solution as the ocean is an unfamiliar territory and they are familiar with their ways on land. Life on the water would also be incredibly different, with limited personal living space and many more shared spaced instead. There is also the threat of possible overfishing of nearby and local species to the colony, and also the raised question of waste disposal. With limited ability of fresh water availability, due to the inability to drill or stream it, critics and theorists of the idea themselves suggest and acknowledge that ocean colonies are unable to ever be purely self-sufficient.

Progress

Land reclamation, followed by Seasteading, are the two technologies leading the way in terms of development plans.

In 2017, the Seasteading Institute proposed to begin building the first project village by 2020 in a lagoon in Tahiti. Investor in the project, John Quirk, stated in 2018, that “we could conceivably see our first modest seastead for 300 people by 2022”.

In terms of law, in 2019, plans were passed allowing a nation to host the first seastead, to which it must adhere to the regulations of that host country but is also liable for its own tailored ‘Special Economic Zone’. Economic freedom is likely to be sought after and granted, but more gradually through a staged approach called ‘strategic incrementalism’.

As of May 2020, both the Seastead Institute and Blue Frontiers have completed their impact assessments and are waiting for updates on their proposal.

Interplanetary Internet

From Wikipedia, the free encyclopedia

 https://en.wikipedia.org/wiki/Interplanetary_Internet

 

The speed of light, illustrated here by a beam of light traveling from Earth to the Moon, would limit the speed at which messages would be able to travel in the interplanetary Internet. In this example, it takes light 1.26 seconds to travel from the Earth to the Moon. Due to the vast distances involved, much longer delays may be incurred than in the Earth-bound Internet.

 

Computer network types by spatial scope
Nanoscale Near-field (NFC) Body Personal (PAN) Near-me Local (LAN) Storage (SAN) Wireless (WLAN) Virtual (VLAN) Home (HAN) Building Campus (CAN) Backbone Metropolitan (MAN) Municipal wireless (MWN) Wide (WAN) Cloud Internet Interplanetary Internet

Internet
An Opte Project visualization of routing paths through a portion of the Internet

General Access Activism Censorship Data activism Democracy Digital divide Digital rights Freedom Freedom of information Internet phenomena Net neutrality Privacy Right to Internet access Slacktivism Sociology Usage Vigilantism Virtual community Virtual volunteering

Governance IGF NRO IANA ICANN IETF ISOC

Information infrastructure Domain Name System Hypertext Transfer Protocol Internet exchange point Internet protocol suite Internet Protocol Transmission Control Protocol Internet service provider IP address Internet Message Access Protocol Simple Mail Transfer Protocol

Services Blogs Microblogging Email Fax File sharing File transfer Games Instant messaging Podcasts Shopping Television Voice over IP World Wide Web search

History History of the Internet Oldest domain names Pioneers Protocol Wars

Guides Index Outline

Internet portal

Simplified Interplanetary Internet overview, Mars to Earth communication

The interplanetary Internet is a conceived computer network in space, consisting of a set of network nodes that can communicate with each other. These nodes are the planet's orbiters (satellites) and landers (e.g., Curiosity Rover, robots), and the earth ground stations. For example, the orbiters collect the scientific data from the Curiosity rover on Mars through near-Mars communication links, transmit the data to Earth through direct links from the Mars orbiters to the Earth ground stations, and finally the data can be routed through Earth's internal internet.

Interplanetary communication is greatly delayed by interplanetary distances, so a new set of protocols and technology that are tolerant to large delays and errors are required. The interplanetary Internet is a store and forward network of internets that is often disconnected, has a wireless backbone fraught with error-prone links and delays ranging from tens of minutes to even hours, even when there is a connection.

Challenges and reasons

In the core implementation of Interplanetary Internet, satellites orbiting a planet communicate to other planet's satellites. Simultaneously, these planets revolve around the Sun with long distances, and thus many challenges face the communications. The reasons and the resultant challenges are:

1. The motion and long distances between planets: The interplanetary communication is greatly delayed due to the interplanetary distances and the motion of the planets. The delay is variable and long, ranges from a couple of minutes (Earth-to-Mars), to a couple of hours (Pluto-to-Earth), depending on their relative positions. The interplanetary communication also suspends due to the solar conjunction, when the sun's radiation hinders the direct communication between the planets. As such, the communication characterizes lossy links and intermittent link connectivity.
2. Low embeddable payload: Satellites can only carry a small payload, which poses challenges to the power, mass, size, and cost for communication hardware design. An asymmetric bandwidth would be the result of this limitation. This asymmetry reaches ratios up to 1000:1 as downlink:uplink bandwidth portion.
3. Absence of fixed infrastructure: The graph of participating nodes in a specific planet to a specific planet communication keeps changing over time, due to the constant motion. The routes of the planet-to-planet communication are planned and scheduled rather than being opportunistic.

The Interplanetary Internet design must address these challenges to operate successfully and achieve good communication with other planets. It also must use the few available resources efficiently in the system.

Development

Space communication technology has steadily evolved from expensive, one-of-a-kind point-to-point architectures, to the re-use of technology on successive missions, to the development of standard protocols agreed upon by space agencies of many countries. This last phase has gone on since 1982 through the efforts of the Consultative Committee for Space Data Systems (CCSDS), a body composed of the major space agencies of the world. It has 11 member agencies, 32 observer agencies, and over 119 industrial associates.

The evolution of space data system standards has gone on in parallel with the evolution of the Internet, with conceptual cross-pollination where fruitful, but largely as a separate evolution. Since the late 1990s, familiar Internet protocols and CCSDS space link protocols have integrated and converged in several ways; for example, the successful FTP file transfer to Earth-orbiting STRV 1B on January 2, 1996, which ran FTP over the CCSDS IPv4-like Space Communications Protocol Specifications (SCPS) protocols. Internet Protocol use without CCSDS has taken place on spacecraft, e.g., demonstrations on the UoSAT-12 satellite, and operationally on the Disaster Monitoring Constellation. Having reached the era where networking and IP on board spacecraft have been shown to be feasible and reliable, a forward-looking study of the bigger picture was the next phase.

ICANN meeting, Los Angeles, USA, 2007. The marquee pays a humorous homage to the Ed Wood film Plan 9 from Outer Space (1959), and the operating system Plan 9 from Bell Labs, while namedropping Internet pioneer Vint Cerf using a spoof of a then-current film Surf's Up (2007).

The Interplanetary Internet study at NASA's Jet Propulsion Laboratory (JPL) was started by a team of scientists at JPL led by Vinton Cerf and the late Adrian Hooke.^[12] Cerf is one of the pioneers of the Internet on Earth, and was appointed as a distinguished visiting scientist at JPL in 1998. Hooke was one of the founders and directors of CCSDS.

While IP-like SCPS protocols are feasible for short hops, such as ground station to orbiter, rover to lander, lander to orbiter, probe to flyby, and so on, delay-tolerant networking is needed to get information from one region of the Solar System to another. It becomes apparent that the concept of a region is a natural architectural factoring of the Interplanetary Internet.

A region is an area where the characteristics of communication are the same. Region characteristics include communications, security, the maintenance of resources, perhaps ownership, and other factors. The Interplanetary Internet is a "network of regional internets".

What is needed then, is a standard way to achieve end-to-end communication through multiple regions in a disconnected, variable-delay environment using a generalized suite of protocols. Examples of regions might include the terrestrial Internet as a region, a region on the surface of the Moon or Mars, or a ground-to-orbit region.

The recognition of this requirement led to the concept of a "bundle" as a high-level way to address the generalized Store-and-Forward problem. Bundles are an area of new protocol development in the upper layers of the OSI model, above the Transport Layer with the goal of addressing the issue of bundling store-and-forward information so that it can reliably traverse radically dissimilar environments constituting a "network of regional internets".

Delay-tolerant networking (DTN) was designed to enable standardized communications over long distances and through time delays. At its core is something called the Bundle Protocol (BP), which is similar to the Internet Protocol, or IP, that serves as the heart of the Internet here on Earth. The big difference between the regular Internet Protocol (IP) and the Bundle Protocol is that IP assumes a seamless end-to-end data path, while BP is built to account for errors and disconnections — glitches that commonly plague deep-space communications.

Bundle Service Layering, implemented as the Bundling protocol suite for delay-tolerant networking, will provide general-purpose delay-tolerant protocol services in support of a range of applications: custody transfer, segmentation and reassembly, end-to-end reliability, end-to-end security, and end-to-end routing among them. The Bundle Protocol was first tested in space on the UK-DMC satellite in 2008.

The Deep Impact mission.

An example of one of these end-to-end applications flown on a space mission is the CCSDS File Delivery Protocol (CFDP), used on the Deep Impact comet mission. CFDP is an international standard for automatic, reliable file transfer in both directions. CFDP should not be confused with Coherent File Distribution Protocol, which has the same acronym and is an IETF-documented experimental protocol for rapidly deploying files to multiple targets in a highly networked environment.

In addition to reliably copying a file from one entity (such as a spacecraft or ground station) to another entity, CFDP has the capability to reliably transmit arbitrary small messages defined by the user, in the metadata accompanying the file, and to reliably transmit commands relating to file system management that are to be executed automatically on the remote end-point entity (such as a spacecraft) upon successful reception of a file.

Protocol

The Consultative Committee for Space Data Systems (CCSDS) packet telemetry standard defines the protocol used for the transmission of spacecraft instrument data over the deep-space channel. Under this standard, an image or other data sent from a spacecraft instrument is transmitted using one or more packets.

CCSDS packet definition

A packet is a block of data with length that can vary between successive packets, ranging from 7 to 65,542 bytes, including the packet header.

• Packetized data is transmitted via frames, which are fixed-length data blocks. The size of a frame, including frame header and control information, can range up to 2048 bytes.
• Packet sizes are fixed during the development phase.

Because packet lengths are variable but frame lengths are fixed, packet boundaries usually do not coincide with frame boundaries.

Telecom processing notes

Data in a frame is typically protected from channel errors by error-correcting codes.

• Even when the channel errors exceed the correction capability of the error-correcting code, the presence of errors is nearly always detected by the error-correcting code or by a separate error-detecting code.
• Frames for which uncorrectable errors are detected are marked as undecodable and typically are deleted.

Handling data loss

Deleted undecodable whole frames are the principal type of data loss that affects compressed data sets. In general, there would be little to gain from attempting to use compressed data from a frame marked as undecodable.

• When errors are present in a frame, the bits of the subband pixels are already decoded before the first bit error will remain intact, but all subsequent decoded bits in the segment usually will be completely corrupted; a single bit error is often just as disruptive as many bit errors.
• Furthermore, compressed data usually are protected by powerful, long-blocklength error-correcting codes, which are the types of codes most likely to yield substantial fractions of bit errors throughout those frames that are undecodable.

Thus, frames with detected errors would be essentially unusable even if they were not deleted by the frame processor.

This data loss can be compensated for with the following mechanisms.

• If an erroneous frame escapes detection, the decompressor will blindly use the frame data as if they were reliable, whereas in the case of detected erroneous frames, the decompressor can base its reconstruction on incomplete, but not misleading, data.
• However, it is extremely rare for an erroneous frame to go undetected.
• For frames coded by the CCSDS Reed–Solomon code, fewer than 1 in 40,000 erroneous frames can escape detection.
• All frames not employing the Reed–Solomon code use a cyclic redundancy check (CRC) error-detecting code, which has an undetected frame-error rate of less than 1 in 32,000.

Implementation

The InterPlanetary Internet Special Interest Group of the Internet Society has worked on defining protocols and standards that would make the IPN possible. The Delay-Tolerant Networking Research Group (DTNRG) is the primary group researching Delay-tolerant networking (DTN). Additional research efforts focus on various uses of the new technology.

The canceled Mars Telecommunications Orbiter had been planned to establish an Interplanetary Internet link between Earth and Mars, in order to support other Mars missions. Rather than using RF, it would have used optical communications using laser beams for their higher data rates. "Lasercom sends information using beams of light and optical elements, such as telescopes and optical amplifiers, rather than RF signals, amplifiers, and antennas"

NASA JPL tested the DTN protocol with their Deep Impact Networking (DINET) experiment on board the Deep Impact/EPOXI spacecraft in October, 2008.

In May 2009, DTN was deployed to a payload on board the ISS. NASA and BioServe Space Technologies, a research group at the University of Colorado, have been continuously testing DTN on two Commercial Generic Bioprocessing Apparatus (CGBA) payloads. CGBA-4 and CGBA-5 serve as computational and communications platforms which are remotely controlled from BioServe's Payload Operations Control Center (POCC) in Boulder, CO. In October 2012 ISS Station commander Sunita Williams remotely operated Mocup (Meteron Operations and Communications Prototype), a "cat-sized" Lego Mindstorms robot fitted with a BeagleBoard computer and webcam, located in the European Space Operations Centre in Germany in an experiment using DTN. These initial experiments provide insight into future missions where DTN will enable the extension of networks into deep space to explore other planets and solar system points of interest. Seen as necessary for space exploration, DTN enables timeliness of data return from operating assets which results in reduced risk and cost, increased crew safety, and improved operational awareness and science return for NASA and additional space agencies.

DTN has several major arenas of application, in addition to the Interplanetary Internet, which include sensor networks, military and tactical communications, disaster recovery, hostile environments, mobile devices and remote outposts. As an example of a remote outpost, imagine an isolated Arctic village, or a faraway island, with electricity, one or more computers, but no communication connectivity. With the addition of a simple wireless hotspot in the village, plus DTN-enabled devices on, say, dog sleds or fishing boats, a resident would be able to check their e-mail or click on a Wikipedia article, and have their requests forwarded to the nearest networked location on the sled's or boat's next visit, and get the replies on its return.

Earth orbit

Earth orbit is sufficiently nearby that conventional protocols can be used. For example, the International Space Station has been connected to the regular terrestrial Internet since January 22, 2010 when the first unassisted tweet was posted. However, the space station also serves as a useful platform to develop, experiment, and implement systems that make up the interplanetary Internet. NASA and the European Space Agency (ESA) have used an experimental version of the interplanetary Internet to control an educational rover, placed at the European Space Operations Centre in Darmstadt, Germany, from the International Space Station. The experiment used the DTN protocol to demonstrate technology that one day could enable Internet-like communications that can support habitats or infrastructure on another planet.

Atmosphere of Mars

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Atmosphere_of_Mars 

Atmosphere of Mars

Image of Mars with sandstorm visible, taken by the Hubble Space Telescope on 28 October 2005
General information
Average surface pressure	610 Pa (0.088 psi; 4.6 mmHg; 0.0060 atm)
Mass	2.5x1016 kg
Composition
Carbon dioxide	95%
Nitrogen	2.8%
Argon	2%
Oxygen	0.174%
Carbon monoxide	0.0747%
Water vapor	0.03% (variable)

 

 

Principal components of the Martian atmosphere

Carbon dioxide

 

Molecular nitrogen

 

Argon

The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.8%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and noble gases. The atmosphere of Mars is much thinner than Earth's. The average surface pressure is only about 610 pascals (0.088 psi) which is less than 1% of the Earth's value. The currently thin Martian atmosphere prohibits the existence of liquid water on the surface of Mars, but many studies suggest that the Martian atmosphere was much thicker in the past. The higher density during spring and fall is reduced by 25% during the winter when carbon dioxide partly freezes at the pole caps. The highest atmospheric density on Mars is equal to the density found 35 km (22 mi) above the Earth's surface and is ~0.020 kg/m³. The atmosphere of Mars has been losing mass to space since the planet's core slowed down, and the leakage of gases still continues today.

The atmosphere of Mars is colder than Earth's. Owing to the larger distance from the Sun, Mars receives less solar energy and has a lower effective temperature, which is about 210 K (−63 °C; −82 °F). The average surface emission temperature of Mars is just 215 K (−58 °C; −73 °F), which is comparable to inland Antarctica. The weaker greenhouse effect in the Martian atmosphere (5 °C (9.0 °F), versus 33 °C (59 °F) on Earth) can be explained by the low abundance of other greenhouse gases. The daily range of temperature in the lower atmosphere is huge due to the low thermal inertia; it can range from −75 °C (−103 °F) to near 0 °C (32 °F) near the surface in some regions. The temperature of the upper part of the Martian atmosphere is also significantly lower than Earth's because of the absence of stratospheric ozone and the radiative cooling effect of carbon dioxide at higher altitudes.

Dust devils and dust storms are prevalent on Mars, which are sometimes observable by telescopes from Earth, and in 2018 even with the naked eye as a change in colour and brightness of the planet. Planet-encircling dust storms (global dust storms) occur on average every 5.5 Earth years (every 3 Martian years) on Mars and can threaten the operation of Mars rovers. However, the mechanism responsible for the development of large dust storms is still not well understood. It has been suggested to be loosely related to gravitational influence of both moons, somewhat similar to the creation of tides on Earth.

The Martian atmosphere is an oxidizing atmosphere. The photochemical reactions in the atmosphere tend to oxidize the organic species and turn them into carbon dioxide or carbon monoxide. Although the most sensitive methane probe on the recently launched ExoMars Trace Gas Orbiter failed to find methane in the atmosphere over the whole of Mars, several previous missions and ground-based telescope detected unexpected levels of methane in the Martian atmosphere, which may even be a biosignature for life on Mars. However, the interpretation of the measurements is still highly controversial and lacks a scientific consensus.

History of atmospheric observations

Main article: History of Mars observation

In 1784, German-born British astronomer William Herschel published an article about his observations of the Martian atmosphere in Philosophical Transactions and noted the occasional movement of a brighter region on Mars, which he attributed to clouds and vapors. In 1809, French astronomer Honoré Flaugergues wrote about his observation of "yellow clouds" on Mars, which are likely to be dust storm events. In 1864, William Rutter Dawes observed that "the ruddy tint of the planet does not arise from any peculiarity of its atmosphere; it seems to be fully proved by the fact that the redness is always deepest near the centre, where the atmosphere is thinnest." Spectroscopic observations in the 1860s and 1870s led many to think the atmosphere of Mars is similar to Earth's. In 1894, though, spectral analysis and other qualitative observations by William Wallace Campbell suggested Mars resembles the Moon, which has no appreciable atmosphere, in many respects. In 1926, photographic observations by William Hammond Wright at the Lick Observatory allowed Donald Howard Menzel to discover quantitative evidence of Mars's atmosphere.

With an enhanced understanding of optical properties of atmospheric gases and advancement in spectrometer technology, scientists started to measure the composition of the Martian atmosphere in the mid-20th century. Lewis David Kaplan and his team detected the signals of water vapor and carbon dioxide in the spectrogram of Mars in 1964, as well as carbon monoxide in 1969. In 1965, the measurements made during Mariner 4's flyby confirmed that the Martian atmosphere is constituted mostly of carbon dioxide, and the surface pressure is about 400 to 700 Pa. After the composition of the Martian atmosphere was known, astrobiological research began on Earth to determine the viability of life on Mars. Containers that simulated environmental conditions on Mars, called "Mars jars", were developed for this purpose.

In 1976, two landers of the Viking program provided the first ever in-situ measurements of the composition of the Martian atmosphere. Another objective of the mission included investigations for evidence of past or present life on Mars (see Viking lander biological experiments). Since then, many orbiters and landers have been sent to Mars to measure different properties of the Martian atmosphere, such as concentration of trace gases and isotopic ratios. In addition, telescopic observations and analysis of Martian meteorites provide independent sources of information to verify the findings. The imageries and measurements made by these spacecraft greatly improve our understanding of the atmospheric processes outside Earth. The rover Curiosity and the lander InSight are still operating on the surface of Mars to carry out experiments and report the local daily weather. The rover Perseverance and helicopter Ingenuity, which formed the Mars 2020 program, landed in February 2021. The rover Rosalind Franklin is scheduled to launch in 2022.

Current chemical composition

Carbon dioxide

See also: Martian polar ice caps

CO₂ is the main component of the Martian atmosphere. It has a mean volume ratio of 94.9%. In winter polar regions, the surface temperature can be lower than the frost point of CO_2. CO₂ gas in the atmosphere can condense on the surface to form 1–2 m thick solid dry ice. In summer, the polar dry ice cap can undergo sublimation and release the CO₂ back to the atmosphere. As a result, significant annual variability in atmospheric pressure (≈25%) and atmospheric composition can be observed on Mars. The condensation process can be approximated by the Clausius–Clapeyron relation for CO₂.

Comparison of the abundance of carbon dioxide, nitrogen, and argon in the atmospheres of Earth, Venus, and Mars

Despite the high concentration of CO₂ in the Martian atmosphere, the greenhouse effect is relatively weak on Mars (about 5 °C) because of the low concentration of water vapor and low atmospheric pressure. While water vapor in Earth's atmosphere has the largest contribution to greenhouse effect on modern Earth, it is present in only very low concentration in the Martian atmosphere. Moreover, under low atmospheric pressure, greenhouse gases cannot absorb infrared radiation effectively because the pressure-broadening effect is weak.

In the presence of solar UV radiation (hν, photons with wavelength shorter than 225 nm), CO₂ in the Martian atmosphere can be photolyzed via the following reaction:

CO₂ + hν (λ < 225 nm) ⟶ CO + O.

If there is no chemical production of CO₂, all the CO₂ in the current Martian atmosphere would be removed by photolysis in about 3,500 years. The hydroxyl radicals (OH) produced from the photolysis of water vapor, together with the other odd hydrogen species (e.g. H, HO₂), can convert carbon monoxide (CO) back to CO₂. The reaction cycle can be described as:

CO + OH ⟶ CO₂ + H

H + O₂ + M ⟶ HO₂ + M

HO₂ + O ⟶ OH + O₂

Net: CO + O ⟶ CO₂

Mixing also plays a role in regenerating CO₂ by bringing the O, CO, and O₂ in the upper atmosphere downward. The balance between photolysis and redox production keeps the average concentration of CO₂ stable in the modern Martian atmosphere.

CO₂ ice clouds can form in winter polar regions and at very high altitudes (>50 km) in tropical regions, where the air temperature is lower than the frost point of CO₂.

Nitrogen

N₂ is the second most abundant gas in the Martian atmosphere. It has a mean volume ratio of 2.6%. Various measurements showed that the Martian atmosphere is enriched in ¹⁵N. The enrichment of heavy isotopes of nitrogen is possibly caused by mass-selective escape processes.

Argon isotope ratios are a signature of atmospheric loss on Mars.

Argon

Argon is the third most abundant gas in the Martian atmosphere. It has a mean volume ratio of 1.9%. In terms of stable isotopes, Mars is enriched in ³⁸Ar relative to ³⁶Ar, which can be attributed to hydrodynamic escape.

One of Argon's isotopes, ⁴⁰Ar, is produced from the radioactive decay of ⁴⁰K. In contrast, ³⁶Ar is primordial: It was present in the atmosphere after the formation of Mars. Observations indicate that Mars is enriched in ⁴⁰Ar relative to ³⁶Ar, which cannot be attributed to mass-selective loss processes. A possible explanation for the enrichment is that a significant amount of primordial atmosphere, including ³⁶Ar, was lost by impact erosion in the early history of Mars, while ⁴⁰Ar was emitted to the atmosphere after the impact.

Seasonal variations of oxygen at Gale crater

Oxygen and ozone

The estimated mean volume ratio of molecular oxygen (O₂) in the Martian atmosphere is 0.174%. It is one of the products of the photolysis of CO₂, water vapor, and ozone (O₃). It can react with atomic oxygen (O) to re-form ozone (O₃). In 2010, the Herschel Space Observatory detected molecular oxygen in the Martian atmosphere.

Atomic oxygen is produced by photolysis of CO₂ in the upper atmosphere and can escape the atmosphere via dissociative recombination or ion pickup. In early 2016, Stratospheric Observatory for Infrared Astronomy (SOFIA) detected atomic oxygen in the atmosphere of Mars, which has not been found since the Viking and Mariner mission in the 1970s.

In 2019, Nasa scientists working on the Curiosity rover mission, who have been taking measurements of the gas, discovered that the amount of oxygen in the Martian atmosphere rose by 30% in spring and summer.

Similar to stratospheric ozone in Earth's atmosphere, the ozone present in the Martian atmosphere can be destroyed by catalytic cycles involving odd hydrogen species:

H + O₃ ⟶ OH + O₂

O + OH ⟶ H + O₂

Net: O + O₃ ⟶  2O₂

Since water is an important source of these odd hydrogen species, higher abundance of ozone is usually observed in the regions with lower water vapor content. Measurements showed that the total column of ozone can reach 2–30 μm-atm around the poles in winter and spring, where the air is cold and has low water saturation ratio. The actual reactions between ozone and odd hydrogen species may be further complicated by the heterogeneous reactions that take place in water-ice clouds.

It is thought that the vertical distribution and seasonality of ozone in the Martian atmosphere is driven by the complex interactions between chemistry and transport of oxygen-rich air from sunlit latitudes to the poles. The UV/IR spectrometer on Mars Express (SPICAM) has shown the presence of two distinct ozone layers at low-to-mid latitudes. These comprise a persistent, near-surface layer below an altitude of 30 km (19 mi), a separate layer that is only present in northern spring and summer with an altitude varying from 30 to 60 km, and another separate layer that exists 40–60 km above the southern pole in winter, with no counterpart above the Mars's north pole. This third ozone layer shows an abrupt decrease in elevation between 75 and 50 degrees south. SPICAM detected a gradual increase in ozone concentration at 50 km (31 mi) until midwinter, after which it slowly decreased to very low concentrations, with no layer detectable above 35 km (22 mi).

Water vapor

See also: Water on Mars and Martian polar ice caps

Water vapor is a trace gas in the Martian atmosphere and has huge spatial, diurnal and seasonal variability. Measurements made by Viking orbiter in the late 1970s suggested that the entire global total mass of water vapor is equivalent to about 1 to 2 km³ of ice. More recent measurements by Mars Express orbiter showed that the globally annually-averaged column abundance of water vapor is about 10-20 precipitable microns (pr. μm). Maximum abundance of water vapor (50-70 pr. μm) is found in the northern polar regions in early summer due to the sublimation of water ice in the polar cap.

Unlike in Earth's atmosphere, liquid-water clouds cannot exist in the Martian atmosphere; this is because of the low atmospheric pressure. Cirrus-like water-ice clouds have been observed by the cameras on Opportunity rover and Phoenix lander. Measurements made by the Phoenix lander showed that water-ice clouds can form at the top of the planetary boundary layer at night and precipitate back to the surface as ice crystals in the northern polar region.

Dust

See also: mineral dust and Martian soil § Atmospheric dust

Under sufficiently strong wind (> 30 ms⁻¹), dust particles can be mobilized and lifted from the surface to the atmosphere. Some of the dust particles can be suspended in the atmosphere and travel by circulation before falling back to the ground. Dust particles can attenuate solar radiation and interact with infrared radiation, which can lead to a significant radiative effect on Mars. Orbiter measurements suggest that the globally-averaged dust optical depth has a background level of 0.15 and peaks in the perihelion season (southern spring and summer). The local abundance of dust varies greatly by seasons and years. During global dust events, Mars surface assets can observe optical depth that is over 4. Surface measurements also showed the effective radius of dust particles ranges from 0.6 μm to 2 μm and has considerable seasonality.

Dust has an uneven vertical distribution on Mars. Apart from the planetary boundary layer, sounding data showed that there are other peaks of dust mixing ratio at the higher altitude (e.g. 15–30 km above the surface).

Seasonal variations in oxygen and methane at Gale crater

Methane

Main article: Methane on Mars

As a volcanic and biogenic species, methane is of interest to geologists and astrobiologists. However, methane is chemically unstable in an oxidizing atmosphere with UV radiation. The lifetime of methane in the Martian atmosphere is about 400 years. The detection of methane in a planetary atmosphere may indicate the presence of recent geological activities or living organisms. Since 2004, trace amounts of methane (range from 60 ppb to under detection limit (< 0.05 ppb)) have been reported in various missions and observational studies. The source of methane on Mars and the explanation for the enormous discrepancy in the observed methane concentrations are still under active debate.

See also the section "detection of methane in the atmosphere" for more details.

Sulfur dioxide

Sulfur dioxide (SO₂) in the atmosphere would be an indicator of current volcanic activity. It has become especially interesting due to the long-standing controversy of methane on Mars. If volcanoes have been active in recent Martian history, it would be expected to find SO₂ together with methane in the current Martian atmosphere. No SO₂ has been detected in the atmosphere, with a sensitivity upper limit set at 0.2 ppb. However, a team led by scientists at NASA Goddard Space Flight Center reported detection of SO₂ in Rocknest soil samples analyzed by the Curiosity rover in March 2013.

Other trace gases

Carbon monoxide (CO) is produced by the photolysis of CO₂ and quickly reacts with the oxidants in the Martian atmosphere to re-form CO₂. The estimated mean volume ratio of CO in the Martian atmosphere is 0.0747%.

Noble gases, other than helium and argon, are present at trace levels (≈10 - 0.01 ppmv) in the Martian atmosphere. The concentration of helium, neon, krypton and xenon in the Martian atmosphere has been measured by different missions. The isotopic ratios of noble gases reveal information about the early geological activities on Mars and the evolution of its atmosphere.

Molecular hydrogen (H₂) is produced by the reaction between odd hydrogen species in the middle atmosphere. It can be delivered to the upper atmosphere by mixing or diffusion, decompose to atomic hydrogen (H) by solar radiation and escape the Martian atmosphere. Photochemical modeling estimated that the mixing ratio of H₂ in the lower atmosphere is about 15 ±5 ppmv.

Vertical structure

The vertical structure of the atmosphere of Mars overlaying with temperature profiles retrieved from the entry probes of Mars landers. Data source: NASA Planetary Data System

The vertical temperature structure of the Martian atmosphere differs from Earth's atmosphere in many ways. Information about the vertical structure is usually inferred by using the observations from thermal infrared soundings, radio occultation, aerobraking, landers' entry profiles. Mars's atmosphere can be classified into three layers according to the average temperature profile:

• Troposphere (≈0–40 km): The layer where most of the weather phenomena (e.g. convection and dust storms) take place. Its dynamics is heavily driven by the daytime surface heating and the amount of suspended dust. Mars has a higher scale height of 11.1 km than Earth (8.5 km) because of its weaker gravity. The theoretical dry adiabatic lapse rate of Mars is 4.3 °C km⁻¹, but the measured average lapse rate is about 2.5 °C km⁻¹ because the suspended dust particles absorb solar radiation and heat the air. The planetary boundary layer can extend to over 10 km thick during the daytime. The near-surface diurnal temperature range is huge (60 °C) due to the low thermal inertia. Under dusty conditions, the suspended dust particles can reduce the surface diurnal temperature range to only 5 °C. The temperature above 15 km is controlled by radiative processes instead of convection. Mars is also a rare exception to the "0.1-bar tropopause" rule found in the other atmospheres in solar system.
• Mesosphere (≈40–100 km): The layer that has the lowest temperature. CO₂ in the mesosphere acts as a cooling agent by efficiently radiating heat into space. Stellar occultation observations show that the mesopause of Mars locates at about 100 km (around 0.01 to 0.001 Pa level) and has a temperature of 100-120 K. The temperature can sometimes be lower than the frost point of CO₂, and detections of CO₂ ice clouds in the Martian mesosphere have been reported.
• Thermosphere (≈100–230 km): The layer is mainly controlled by extreme UV heating. The temperature of the Martian thermosphere increases with altitude and varies by season. The daytime temperature of the upper thermosphere ranges from 175 K (at aphelion) to 240 K (at perihelion) and can reach up to 390 K, but it is still significantly lower than the temperature of Earth's thermosphere. The higher concentration of CO₂ in the Martian thermosphere may explain part of the discrepancy because of the cooling effects of CO₂ in high altitude. It is thought that auroral heating processes is not important in the Martian thermosphere because of the absence of a strong magnetic field in Mars, but the MAVEN orbiter has detected several aurora events.

Mars does not have a persistent stratosphere due to the lack of shortwave-absorbing species in its middle atmosphere (e.g. stratospheric ozone in Earth's atmosphere and organic haze in Jupiter's atmosphere) for creating a temperature inversion. However, a seasonal ozone layer and a strong temperature inversion in the middle atmosphere have been observed over the Martian south pole. The altitude of the turbopause of Mars varies greatly from 60 to 140 km, and the variability is driven by the CO₂ density in the lower thermosphere. Mars also has a complicated ionosphere that interacts with the solar wind particles, extreme UV radiation and X-rays from Sun, and the magnetic field of its crust. The exosphere of Mars starts at about 230 km and gradually merges with interplanetary space.

Dust and other dynamic features

Dust devils

See also: Dust devil § Martian dust devils

Dust devils are common on Mars. Like their counterparts on Earth, dust devils form when the convective vortices driven by strong surface heating are loaded with dust particles. Dust devils on Mars usually have a diameter of tens of meter and height of several kilometers, which are much taller than the ones observed on Earth. Study of dust devils' tracks showed that most of Martian dust devils occur at around 60°N and 60°S in spring and summer. They lift about 2.3 × 10¹¹ kg of dust from land surface to atmosphere annually, which is comparable to the contribution from local and regional dust storms.

Dust storms

Local and regional dust storms are not rare on Mars. Local storms have a size of about 10³ km² and occurrence of about 2000 events per Martian year, while regional storms of 10⁶ km² large are observed frequently in southern spring and summer. Near the polar cap, dust storms sometimes can be generated by frontal activities and extratropical cyclones.

Global dust storms (area > 10⁶ km² ) occur on average once every 3 Martian years. Observations showed that larger dust storms are usually the result of merging smaller dust storms, but the growth mechanism of the storm and the role of atmospheric feedbacks are still not well understood. Although it is thought that Martian dust can be entrained into the atmosphere by processes similar to Earth's (e.g. saltation), the actual mechanisms are yet to be verified, and electrostatic or magnetic forces may also play in modulating dust emission. Researchers reported that the largest single source of dust on Mars comes from the Medusae Fossae Formation.

On 1 June 2018, NASA scientists detected signs of a dust storm (see image) on Mars which resulted in the end of the solar-powered Opportunity rover's mission since the dust blocked the sunlight (see image) needed to operate. By 12 June, the storm was the most extensive recorded at the surface of the planet, and spanned an area about the size of North America and Russia combined (about a quarter of the planet). By 13 June, Opportunity rover began experiencing serious communication problems due to the dust storm.

Thermal tides

See also: Atmospheric tide

Solar heating on the day side and radiative cooling on the night side of a planet can induce pressure difference. Thermal tides, which are the wind circulation and waves driven by such a daily-varying pressure field, can explain a lot of variability of the Martian atmosphere. Compared to Earth's atmosphere, thermal tides have a larger influence on the Martian atmosphere because of the stronger diurnal temperature contrast. The surface pressure measured by Mars rovers showed clear signals of thermal tides, although the variation also depends on the shape of the planet's surface and the amount of suspended dust in the atmosphere. The atmospheric waves can also travel vertically and affect the temperature and water-ice content in the middle atmosphere of Mars.

Orographic clouds

See also: Orographic lift § Associated clouds

 

Water-ice clouds formed in the vicinity of the Arsia Mons volcano. The image was taken on 21 September 2018, but similar cloud formation events had been observed in the same site before. Photo credit: ESA/DLR/FU Berlin

On Earth, mountain ranges sometimes force an air mass to rise and cool down. As a result, water vapor becomes saturated and clouds are formed during the lifting process. On Mars, orbiters have observed a seasonally recurrent formation of huge water-ice clouds around the downwind side of the 20 km-high volcanoes Arsia Mons, which is likely caused by the same mechanism.

Wind modification of the surface

On Mars, the near-surface wind is not only emitting dust but also modifying the geomorphology of Mars over long time scales. Although it was thought that the atmosphere of Mars is too thin for mobilizing the sandy features, observations made by HiRSE showed that the migration of dunes is not rare on Mars. The global average migration rate of dunes (2 – 120 m tall) is about 0.5 meter per year. Atmospheric circulation models suggested repeated cycles of wind erosion and dust deposition can lead, possibly, to a net transport of soil materials from the lowlands to the uplands on geological timescales.

Movement of sandy features in Nili Patera dune field on Mars detected by HiRISE. Photo credit: NASA/JPL Caltech/U. Arizona/JHU-APL

Acoustic environment

In April 2022, scientists reported, for the first time, studies of sound waves on Mars. These studies were based on measurements by instruments on the Perseverance rover. The scientists found that the speed of sound is slower in the Martian atmosphere, 100 times thinner than the terrestrial atmosphere, than the atmosphere on Earth; the speed of sound on Mars, within the audible bandwidth between 20 Hz - 20 kHz, varies depending on pitch, seemingly due to the low pressure and thermal turbulence of Martian surface air; and, as a result of these unique Martian conditions, sound is much quieter, and live music would be more variable, than on Earth.

Atmospheric evolution

See also: Atmospheric escape and Water on Mars

The mass and composition of the Martian atmosphere are thought to have changed over the course of the planet's lifetime. A thicker, warmer and wetter atmosphere is required to explain several apparent features in the earlier history of Mars, such as the existence of liquid water bodies. Observations of the Martian upper atmosphere, measurements of isotopic composition and analyses of Martian meteorites, provide evidence of the long-term changes of the atmosphere and constraints for the relative importance of different processes.

Atmosphere in the early history

Isotopic ratio of different species in Martian and Earth's atmosphere

Isotopic ratio	Mars	Earth	Mars / Earth
D / H (in H2O)	9.3 ± 1.7 ‰	1.56 ‰	~6
12C / 13C	85.1 ± 0.3	89.9	0.95
14N / 15N	173 ± 9	272	0.64
16O / 18O	476 ± 4.0	499	0.95
36Ar / 38Ar	4.2 ± 0.1	5.305 ± 0.008	0.79
40Ar / 36Ar	1900 ± 300	298.56 ± 0.31	~6
C / 84Kr	(4.4–6) × 106	4 × 107	~0.1
129Xe / 132Xe	2.5221 ± 0.0063	0.97	~2.5

In general, the gases found on modern Mars are depleted in lighter stable isotopes, indicating the Martian atmosphere has changed by some mass-selected processes over its history. Scientists often rely on these measurements of isotope composition to reconstruct conditions of the Martian atmosphere in the past.

While Mars and Earth have similar ¹²C / ¹³C and ¹⁶O / ¹⁸O ratios, ¹⁴N is much more depleted in the Martian atmosphere. It is thought that the photochemical escape processes are responsible for the isotopic fractionation and has caused a significant loss of nitrogen on geological timescales. Estimates suggest that the initial partial pressure of N₂ may have been up to 30 hPa.

Hydrodynamic escape in the early history of Mars may explain the isotopic fractionation of argon and xenon. On modern Mars, the atmosphere is not leaking these two noble gases to outer space owing to their heavier mass. However, the higher abundance of hydrogen in the Martian atmosphere and the high fluxes of extreme UV from the young Sun, together could have driven a hydrodynamic outflow and dragged away these heavy gases. Hydrodynamic escape also contributed to the loss of carbon, and models suggest that it is possible to lose 1,000 hPa (1 bar) of CO₂ by hydrodynamic escape in one to ten million years under much stronger solar extreme UV on Mars. Meanwhile, more recent observations made by the MAVEN orbiter suggested that sputtering escape is very important for the escape of heavy gases on the nightside of Mars and could have contributed to 65% loss of argon in the history of Mars.

The Martian atmosphere is particularly prone to impact erosion owing to the low escape velocity of Mars. An early computer model suggested that Mars could have lost 99% of its initial atmosphere by the end of late heavy bombardment period based on a hypothetical bombardment flux estimated from lunar crater density. In terms of relative abundance of carbon, the C / ⁸⁴Kr ratio on Mars is only 10% of that on Earth and Venus. Assuming the three rocky planets have the same initial volatile inventory, then this low C / ⁸⁴Kr ratio implies the mass of CO₂ in the early Martian atmosphere should have been ten times higher than the present value. The huge enrichment of radiogenic ⁴⁰Ar over primordial ³⁶Ar is also consistent with the impact erosion theory.

One of the ways to estimate the amount of water lost by hydrogen escape in the upper atmosphere is to examine the enrichment of deuterium over hydrogen. Isotope-based studies estimate that 12 m to over 30 m global equivalent layer of water has been lost to space via hydrogen escape in Mars' history. It is noted that atmospheric-escape-based approach only provides the lower limit for the estimated early water inventory.

To explain the coexistence of liquid water and faint young Sun during early Mars' history, a much stronger greenhouse effect must have occurred in the Martian atmosphere to warm the surface up above freezing point of water. Carl Sagan first proposed that a 1 bar H₂ atmosphere can produce enough warming for Mars. The hydrogen can be produced by the vigorous outgassing from a highly reduced early Martian mantle and the presence of CO₂ and water vapor can lower the required abundance of H₂ to generate such a greenhouse effect. Nevertheless, photochemical modeling showed that maintaining an atmosphere with this high level of H₂ is difficult. SO₂ has also been one of the proposed effective greenhouse gases in the early history of Mars. However, other studies suggested that high solubility of SO₂, efficient formation of H₂SO₄ aerosol and surface deposition prohibit the long-term build-up of SO₂ in the Martian atmosphere, and hence reduce the potential warming effect of SO₂.

Atmospheric escape on modern Mars

Despite the lower gravity, Jeans escape is not efficient in the modern Martian atmosphere due to the relatively low temperature at the exobase (≈200 K at 200 km altitude). It can only explain the escape of hydrogen from Mars. Other non-thermal processes are needed to explain the observed escape of oxygen, carbon and nitrogen.

Hydrogen escape

Molecular hydrogen (H₂) is produced from the dissociation of H₂O or other hydrogen-containing compounds in the lower atmosphere and diffuses to the exosphere. The exospheric H₂ then decomposes into hydrogen atoms, and the atoms that have sufficient thermal energy can escape from the gravitation of Mars (Jeans escape). The escape of atomic hydrogen is evident from the UV spectrometers on different orbiters. While most studies suggested that the escape of hydrogen is close to diffusion-limited on Mars, more recent studies suggest that the escape rate is modulated by dust storms and has a large seasonality. The estimated escape flux of hydrogen range from 10⁷ cm⁻² s⁻¹ to 10⁹ cm⁻² s⁻¹.

Carbon escape

Photochemistry of CO₂ and CO in ionosphere can produce CO₂⁺ and CO⁺ ions, respectively:

CO₂ + hν ⟶ CO+2 + e⁻

CO + hν ⟶ CO⁺ + e⁻

An ion and an electron can recombine and produce electronic-neutral products. The products gain extra kinetic energy due to the Coulomb attraction between ions and electrons. This process is called dissociative recombination. Dissociative recombination can produce carbon atoms that travel faster than the escape velocity of Mars, and those moving upward can then escape the Martian atmosphere:

CO⁺ + e⁻ ⟶ C + O

CO+2 + e⁻ ⟶ C + O₂

UV photolysis of carbon monoxide is another crucial mechanism for the carbon escape on Mars:

CO + hν (λ < 116  nm) ⟶ C + O.

Other potentially important mechanisms include the sputtering escape of CO₂ and collision of carbon with fast oxygen atoms. The estimated overall escape flux is about 0.6 × 10⁷ cm⁻² s⁻¹ to 2.2 × 10⁷ cm⁻² s⁻¹ and depends heavily on solar activity.

Nitrogen escape

Like carbon, dissociative recombination of N₂⁺ is important for the nitrogen escape on Mars. In addition, other photochemical escape mechanism also play an important role:

N₂ + hν ⟶ N⁺ + N + e⁻

N₂ + e⁻ ⟶ N⁺ + N + 2e⁻

Nitrogen escape rate is very sensitive to the mass of the atom and solar activity. The overall estimated escape rate of ¹⁴N is 4.8 × 10⁵ cm⁻² s⁻¹.

Oxygen escape

Dissociative recombination of CO₂⁺ and O₂⁺ (produced from CO₂⁺ reaction as well) can generate the oxygen atoms that travel fast enough to escape:

CO+2 + e⁻ ⟶ CO + O

CO+2 + O ⟶ O+2 + CO

O+2 + e⁻ ⟶ O + O

However, the observations showed that there are not enough fast oxygen atoms the Martian exosphere as predicted by the dissociative recombination mechanism. Model estimations of oxygen escape rate suggested it can be over 10 times lower than the hydrogen escape rate. Ion pick and sputtering have been suggested as the alternative mechanisms for the oxygen escape, but this model suggests that they are less important than dissociative recombination at present.

Mars's escaping atmosphere—carbon, oxygen, hydrogen—measured by MAVEN's UV spectrograph).

Unexplained phenomena

Detection of methane

Main article: Methane on Mars

Methane (CH₄) is chemically unstable in the current oxidizing atmosphere of Mars. It would quickly break down due to ultraviolet radiation from the Sun and chemical reactions with other gases. Therefore, a persistent presence of methane in the atmosphere may imply the existence of a source to continually replenish the gas.

The ESA-Roscomos Trace Gas Orbiter, which has made the most sensitive measurements of methane in Mars' atmosphere with over 100 global soundings, has found no methane to a detection limit of 0.05 parts per billion (ppb). However, there have been other reports of detection of methane by ground-based telescopes and Curiosity rover. Trace amounts of methane, at the level of several ppb, were first reported in Mars's atmosphere by a team at the NASA Goddard Space Flight Center in 2003. Large differences in the abundances were measured between observations taken in 2003 and 2006, which suggested that the methane was locally concentrated and probably seasonal.

In 2014, NASA reported that the Curiosity rover detected a tenfold increase ('spike') in methane in the atmosphere around it in late 2013 and early 2014. Four measurements taken over two months in this period averaged 7.2 ppb, implying that Mars is episodically producing or releasing methane from an unknown source. Before and after that, readings averaged around one-tenth that level. On 7 June 2018, NASA announced a cyclical seasonal variation in the background level of atmospheric methane.

Curiosity detected a cyclical seasonal variation in atmospheric methane.

The principal candidates for the origin of Mars' methane include non-biological processes such as water-rock reactions, radiolysis of water, and pyrite formation, all of which produce H₂ that could then generate methane and other hydrocarbons via Fischer–Tropsch synthesis with CO and CO₂. It has also been shown that methane could be produced by a process involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars. Living microorganisms, such as methanogens, are another possible source, but no evidence for the presence of such organisms has been found on Mars. There are some suspicions about the detection of methane, which suggests that it may instead be caused by the undocumented terrestrial contamination from the rovers or a misinterpretation of measurement raw data.

Lightning events

In 2009, an Earth-based observational study reported detection of large-scale electric discharge events on Mars and proposed that they are related to lightning discharge in Martian dust storms. However, later observation studies showed that the result is not reproducible using the radar receiver on Mars Express and the Earth-based Allen Telescope Array. A laboratory study showed that the air pressure on Mars is not favorable for charging the dust grains, and thus it is difficult to generate lightning in Martian atmosphere.

Super-rotating jet over the equator

Super-rotation refers to the phenomenon that atmospheric mass has a higher angular velocity than the surface of the planet at the equator, which in principle cannot be driven by inviscid axisymmetric circulations. Assimilated data and general circulation model (GCM) simulation suggest that super-rotating jet can be found in Martian atmosphere during global dust storms, but it is much weaker than the ones observed on slow-rotating planets like Venus and Titan. GCM experiments showed that the thermal tides can play a role in inducing the super-rotating jet. Nevertheless, modeling super-rotation still remains as a challenging topic for planetary scientists.

Potential for use by humans

Main articles: In-situ resource utilization, Terraforming of Mars, and Colonization of Mars

The atmosphere of Mars is a resource of known composition available at any landing site on Mars. It has been proposed that human exploration of Mars could use carbon dioxide (CO₂) from the Martian atmosphere to make methane (CH₄) and use it as rocket fuel for the return mission. Mission studies that propose using the atmosphere in this way include the Mars Direct proposal of Robert Zubrin and the NASA Design Reference Mission study. Two major chemical pathways for use of the carbon dioxide are the Sabatier reaction, converting atmospheric carbon dioxide along with additional hydrogen (H₂), to produce methane (CH₄) and oxygen (O₂), and electrolysis, using a zirconia solid oxide electrolyte to split the carbon dioxide into oxygen (O₂) and carbon monoxide (CO).

In 2021, however, the NASA spaceship Perseverance was able to make oxygen on Mars. The process is complex and takes a lot of time to produce a small amount of oxygen.