Martian lava tubes are volcanic caverns on Mars that are believed to form as a result of fast-moving, basaltic lava flows associated with shield volcanism. [1] Lava tubes usually form when the external surface of the lava channels cools more quickly and forms a hardened crust over subsurface lava flows. [2] The flow eventually ceases and drains out of the tube, leaving a conduit-shaped void space which is usually several meters below the surface. Lava tubes are typically associated with extremely fluid pahoehoe lava. [3] Gravity on mars is about 38% that of Earth's, allowing Martian lava tubes to be much larger in comparison.
Lava tubes and related flow structures were first recognized upon examination of Viking orbiter images, and later identified using orbiter imagery from Mars Odyssey, Mars Global Surveyor, Mars Express, and Mars Reconnaissance Orbiter. [2] Lava tubes can visually be detected two ways. The first is as long sinuous troughs known as rilles, which are believed to be the remains of collapsed lava tubes. The second method of possible identification is through observation of cave "skylights" or pit craters, which appear as dark, nearly circular features on the surface of Mars. [2] [3] In June, 2010, a group of seventh grade science students at Evergreen Middle School in Cottonwood, California, participating in the Mars Student Imaging Project, helped researchers discover a new series of lava tubes near Pavonis Mons through identification of a skylight estimated to be 190×160 meters wide and at least 115 meters deep. [4] It is only the second skylight known to be associated with this volcano. [4] In addition to orbital imagery, lava tubes could be detected through the use of:
There has been increased interest in the identification and investigation of lava tubes because they could present scientists with information regarding the geological, paleohydrological, and supposed biological histories of the planet. [5] When speaking about lunar lava tubes, Dr. William "Red" Whittaker, CEO of Astrobotic Technology, states that "something so unique about the lava tubes is that they are the one destination that combines the trifecta of science, exploration, and resources." [6] Access to uncollapsed sections of lava tubes can be done by entering at the end of rille, through skylights, or by drilling or blasting through the roof of a lava tube. [3] Initial exploration of lava tubes may involve rovers, but with difficult challenges. Traditional skylights have large rubble piles directly below them (as seen in the first figure) which would be an obstacle for the rover. The vertical drop that the rover would have to perform would also have to be taken into consideration, as well as the ability of the rover to remain in communication with assets at the surface or in orbit. [7]
Gravity on Mars is about 38% that of Earth, [8] allowing Martian lava tubes to be much larger in comparison. [9] Lava tubes represent prime locations for direct observation of pristine bedrock where keys to the geological, paleohydrological, and possible biological history of Mars could be found. The surface of Mars experiences extreme temperature fluctuations and receives a high amount of Ionizing radiation due to the lack of a magnetic field and the planet's thin atmosphere, which is about one one-hundredth (or 1 percent) the thickness of Earth's. The thin atmosphere allows Mars to radiate heat energy away more easily, so temperatures near the equator can get up to 21 °C (70 °F) during a summer day, and then drop down to −73 °C (−99 °F) at night. [10] Subsurface conditions on Mars are dramatically more benign than those on the surface, which lead researchers to believe that if life did (or does) exist on Mars, it would most likely be found in these more hospitable environments. [11] Life forms would not only be protected from the high surface temperatures and ultraviolet radiation, but also from wind storms and regolith dust. [1] Martian lava tubes could possibly trap volatiles such as water which is considered essential for life, and may also contain reservoirs of ancient ice since cold air can pool in lava tubes and temperatures remain stable. [3] The ability to tap into these reservoirs may provide dramatic insight into the paleoclimatology and astrobiological histories of Mars. [2]
The discovery of Martian lava tubes has implications for the possibility of past or present life on Mars.
The magnetic and climatic histories of Mars and Earth are extremely different, and would have greatly dictated the evolution of both biospheres. Around four billion years ago, the Martian dynamo shut down following a proposed period when a long-lasting Noachian ocean existed, and when life may have existed at the surface. A sudden and intense increase of solar particles eliminated the atmospheric and hydrological protection, causing the atmosphere to thin and water to retreat from the surface. At this point, life may have sought refuge in subterranean environments such as lava tubes. [5]
A wide range of organisms may have survived in the subsurface, such as chemolithotrophs and lithoautotrophs, and certain extremophiles like halophiles or psychrophiles. [5] Microbes found on Earth have been discovered thriving in near-freezing temperatures and very low-oxygen air. This allows researchers to believe that organisms can live in similar extreme situations such as those on Mars where temperatures are colder and less oxygen is available. [12] Volcanic minerals found in lava tubes could provide a rich source of nutrients to chemosynthetic organisms. [1] Scientists are also interested in gaining access to Martian lava tubes because they could give insight into the processes that led to life on Earth since the geologic rock record is better preserved on Mars. [13]
The interior of lava tubes, along with other subsurface cavities, could prove to be prime locations for future crewed missions to Mars by providing shelter for habitats. [1] These natural caverns have roofs estimated to be tens of meters thick which would provide protection from the extreme conditions that would be experienced on the surface. [3] The habitat would be protected from solar radiation, micrometeorites, extreme temperature fluctuations (ambient temperature is believed to be stable in lava tubes), winds, and regolith dust storms which could pose a threat to human health and technology. These natural shelters would also reduce the landed payload mass for crewed missions which would be economically advantageous. [1]
2001 Mars Odyssey is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectrometers and a thermal imager to detect evidence of past or present water and ice, as well as study the planet's geology and radiation environment. The data Odyssey obtains is intended to help answer the question of whether life once existed on Mars and create a risk-assessment of the radiation that future astronauts on Mars might experience. It also acts as a relay for communications between the Curiosity rover, and previously the Mars Exploration Rovers and Phoenix lander, to Earth. The mission was named as a tribute to Arthur C. Clarke, evoking the name of his and Stanley Kubrick's 1968 film 2001: A Space Odyssey.
Olympus Mons is a large shield volcano on Mars. It is over 21.9 km high as measured by the Mars Orbiter Laser Altimeter (MOLA), about 2.5 times the elevation of Mount Everest above sea level. It is Mars's tallest volcano, its tallest planetary mountain, and is approximately tied with Rheasilvia on Vesta as the tallest mountain currently discovered in the Solar System. It is associated with the volcanic region of Tharsis Montes. It last erupted 25 million years ago.
A lava tube, or pyroduct, is a natural conduit formed by flowing lava from a volcanic vent that moves beneath the hardened surface of a lava flow. If lava in the tube empties, it will leave a cave.
Arsia Mons is the southernmost of three volcanoes on the Tharsis bulge near the equator of the planet Mars. To its north is Pavonis Mons, and north of that is Ascraeus Mons. The tallest volcano in the Solar System, Olympus Mons, is to its northwest. Its name comes from a corresponding albedo feature on a map by Giovanni Schiaparelli, which he named in turn after the legendary Roman forest of Arsia Silva. Historically, it was known as Nodus Gordii before being renamed.
The Caves of Mars Project was an early 2000s program funded through Phase II by the NASA Institute for Advanced Concepts to assess the best place to situate the research and habitation modules that a human mission to Mars would require. The final report was published in mid 2004.
The colonization of Mars is the proposed process of establishing and maintaining control of Martian land for exploitation and the possible settlement of Mars. Most colonization concepts focus on settling, but colonization is a broader ethical concept, which international space law has limited, and national space programs have avoided, focusing on a human mission to Mars to explore the planet. Settlement of Mars would involve migration of humans to the planet, the establishment of long-term human presence, and the exploitation of local resources. Though uncrewed rovers have explored Mars, there have been no crewed missions and there have been no return missions.
The geology of Mars is the scientific study of the surface, crust, and interior of the planet Mars. It emphasizes the composition, structure, history, and physical processes that shape the planet. It is analogous to the field of terrestrial geology. In planetary science, the term geology is used in its broadest sense to mean the study of the solid parts of planets and moons. The term incorporates aspects of geophysics, geochemistry, mineralogy, geodesy, and cartography. A neologism, areology, from the Greek word Arēs (Mars), sometimes appears as a synonym for Mars's geology in the popular media and works of science fiction. The term areology is also used by the Areological Society.
A rover is a planetary surface exploration device designed to move over the rough surface of a planet or other planetary mass celestial bodies. Some rovers have been designed as land vehicles to transport members of a human spaceflight crew; others have been partially or fully autonomous robots. Rovers are typically created to land on another planet via a lander-style spacecraft, tasked to collect information about the terrain, and to take crust samples such as dust, soil, rocks, and even liquids. They are essential tools in space exploration.
Mars is the fourth planet from the Sun. The surface of Mars is orange-red because it is covered in iron(III) oxide dust, giving it the nickname "the Red Planet". Mars is among the brightest objects in Earth's sky, and its high-contrast albedo features have made it a common subject for telescope viewing. It is classified as a terrestrial planet and is the second smallest of the Solar System's planets with a diameter of 6,779 km (4,212 mi). In terms of orbital motion, a Martian solar day (sol) is equal to 24.5 hours, and a Martian solar year is equal to 1.88 Earth years. Mars has two natural satellites that are small and irregular in shape: Phobos and Deimos.
Northern Light was a concept mission for a robotic mission to Mars that would consist of a lander and a rover, being studied by a consortium of Canadian universities, companies and organisations. The primary contractor for the spacecraft was Thoth Technology Inc.
The Mars Astrobiology Explorer-Cacher (MAX-C), also known as Mars 2018 mission, was a NASA concept for a Mars rover mission, proposed to be launched in 2018 together with the European ExoMars rover. The MAX-C rover concept was cancelled in April 2011 due to budget cuts.
Lunar lava tubes are lava tubes on the Moon formed during the eruption of basaltic lava flows. When the surface of a lava flow cools, it hardens and the lava can channel beneath the surface in a tube-shaped passage. Once the flow of lava diminishes, the tube may drain, forming a hollow void. Lunar lava tubes are formed on sloped surfaces that range in angle from 0.4° to 6.5°. These tubes may be as wide as 500 metres (1,600 ft) before they become unstable against gravitational collapse. However, stable tubes may still be disrupted by seismic events or meteoroid bombardment.
Interplanetary contamination refers to biological contamination of a planetary body by a space probe or spacecraft, either deliberate or unintentional.
Seasonal flows on warm Martian slopes are thought to be salty water flows occurring during the warmest months on Mars, or alternatively, dry grains that "flow" downslope of at least 27 degrees.
Terrestrial analogue sites are places on Earth with assumed past or present geological, environmental or biological conditions of a celestial body such as the Moon or Mars. Analogue sites are used in the frame of space exploration to either study geological or biological processes observed on other planets, or to prepare astronauts for surface extra-vehicular activity.
A Mars habitat is a hypothetical place where humans could live on Mars. Mars habitats would have to contend with surface conditions that include almost no oxygen in the air, extreme cold, low pressure, and high radiation. Alternatively, the habitat might be placed underground, which helps solve some problems but creates new difficulties.
ExoLance is a low-cost mission concept that could hitch a ride on other missions to Mars in an effort to look for evidence of subsurface life.
Mars habitability analogue environments on Earth are environments that share potentially relevant astrobiological conditions with Mars. These include sites that are analogues of potential subsurface habitats, and deep subsurface habitats.
Moon Diver is a proposed lunar mission concept by NASA's Jet Propulsion Laboratory that would employ a robotic lander and a – distant coaxial – two-wheeled rover called Axel to investigate the exposed geological layers on the walls of a deep lunar pit.
The International-Mars Ice Mapper (I-MIM) mission is a proposed Mars orbiter being developed by NASA in collaboration with the Japan Aerospace Exploration Agency (JAXA), the Canadian Space Agency (CSA), and the Italian Space Agency (ASI). As the mission concept evolves, there may be opportunities for other space agency and commercial partners to join the mission. The goal of the orbiter is the quantification of extent and volume of water ice in non-polar regions of Mars. The results are intended to support future Mars missions, especially with respect to the search for habitable environments and accessible In situ resource utilization (ISRU) resources. The International-Mars Ice Mapper is an "exploration precursor mission", comparing it to the Lunar Reconnaissance Orbiter (LRO) mission. The mission was envisioned to be launched as early as 2026. However, in March 2022, it was revealed in its fiscal year 2023 budget proposal that the US government would terminate NASA financial support for the Mars Ice Mapper, casting the project's future into uncertainty.