Astrobiology

Mars and a Biosphere

Mars, the fourth planet from the Sun, is currently undergoing a great deal of investigation concerning its capacity for maintaining life.

Learning Objectives

Discuss the Martian biosphere

Key Takeaways

Key Points

  • Mars has a thin atmosphere and its surface is very similar to the Earth’s moon (craters) and has volcanoes, valleys, deserts, and polar ice caps similar to Earth itself. Mars rotates similarly to Earth and has a tilt that produces seasons.
  • Mars was first observed at close proximity in 1965 by the Mariner 4. Scientists hypothesize that the surface of Mars is covered by liquid water.
  • Scientists are still collecting and analyzing data concerning the surface of Mars. The planet is currently host to five functioning spacecraft.
  • A biosphere is an global ecological system that incorporates all living beings and their relationships with the lithosphere, hydrosphere, and atmosphere. A great deal of research is going into developing hypotheses on Martian biosphere. Results are currently inconclusive.

Key Terms

  • Solar System: The Sun and all the heavenly bodies that orbit around it, including the eight planets, their moons, the asteroids, and comets.
  • Mars: The fourth planet in the solar system. Symbol: ♂
  • planet: A body which orbits the Sun directly and is massive enough to be in hydrostatic equilibrium (effectively meaning a spheroid) and to dominate its orbit. The eight planets in the Solar System are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto was considered a planet until 2006 and has now been reclassified as a dwarf planet.

The Planet Mars

Mars is the fourth planet from the Sun and the second smallest planet in the Solar System. The planet can be seen from Earth with the naked eye. Mars has a thin atmosphere and its surface is very similar to the Earth’s moon (craters). Mars has volcanoes, valleys, deserts, and polar ice caps similar to Earth. Additionally, Mars rotates similarly to Earth and has a tilt that produces seasons.

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Mars: This is the true-color view of Mars as seen through NASA’s Hubble Space Telescope in 1999.

Mars was first observed at close proximity in 1965 by the Mariner 4. This observation began decades of study and speculations about the structure of the surface of Mars. Scientists hypothesize that its surface is covered by liquid water. Scientists are still collecting and analyzing data concerning its surface. The planet is currently host to five functioning spacecraft: three in orbit—the Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter; and two on the surface—Mars Exploration Rover Opportunity and the Mars Science Laboratory Curiosity.

Biosphere

A biosphere is typically defined as the part of the Earth and its atmosphere capable of supporting life. A biosphere can also be thought of as an global ecological system that incorporates all living beings and their relationships with the lithosphere, hydrosphere, and atmosphere. Currently, a great deal of research is going into developing hypotheses on a Martian biosphere. This research overlaps greatly with Martian terraforming, which explores how humans might manipulate the Martian environment to make it stable for maintaining life. As mentioned above, scientists are still collecting a great deal of data on the structure and functioning of Mars. This is a burgeoning field of research.

Martian Biosignatures

A biosignature, a substance that provides scientific evidence of past or present life, is present in the form of fog on the planet Mars.

Learning Objectives

Describe biosignatures

Key Takeaways

Key Points

  • A biosignature is any substance – such as an element, isotope, molecule, or phenomenon – that provides scientific evidence of past or present life.
  • On Earth, normal mammalian functioning has produced a fog of chemicals that is not replicated by any chemical process. This mixture of gases has also been observed in the atmosphere of the planet Mars.
  • In the 1970s there were two American probes called Viking I and II that were sent to Mars to explore the planet for life. The Viking landers carried three life-detection experiments that looked for signs of metabolism, but the imaging and life-detection results were inconclusive.
  • There are plans for future missions to Mars to search for more evidence of biosignatures and habitable environments for life.

Key Terms

  • biosignature: Any measurable phenomenon that indicates the presence of life.
  • metabolism: The complete set of chemical reactions that occur in living cells.
  • abiotic: Nonliving, inanimate, characterized by the absence of life; of inorganic matter.

Biosignatures

A biosignature is any substance – such as an element, isotope, molecule, or phenomenon – that provides scientific evidence of past or present life. It is important to understand that while the presence of these substances or events could be a result of past or present life, they are not definitive evidence and should not be treated as such. Scientists determine the significance of a biosignature not only by examining the probability of life creating it, but mostly by the improbability of abiotic processes producing it.

Martian Biosignatures

On Earth, normal mammalian functioning has produced a fog of chemicals that is not replicated by any chemical process. This fog is made up of large amounts of oxygen and small amounts of methane. This mixture of gases has also been observed in the atmosphere of the planet Mars. Due to scientific thought that this fog cannot be formed by a chemical process, logic concludes that there must be some source of life on the planet.

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Martian Meteorite with Possible Fossilized Bacteria: Some researchers suggest that these microscopic structures on the Martian meteorite could be fossilized bacteria.

Scientists feel it is necessary to explore their hypotheses, so in the 1970s there were two American probes called Viking I and II that were sent to Mars to explore for life. The probes took images of the planet while in orbit and also while actually on the surface of Mars. The Viking landers carried three life-detection experiments that looked for signs of metabolism. Unfortunately, the imaging and life-detection results were inconclusive. There are plans for future missions to Mars, the Mars Science Laboratory and ExoMars, which will not only search for biosignatures but try to detect habitable environments as well.

Terraforming Mars

Terraforming Mars is the hypothetical idea that Mars could be altered in such a way to sustain human and terrestrial life forms.

Learning Objectives

Describe terraforming

Key Takeaways

Key Points

  • The phrase “terraforming Mars ” refers to the idea that the planet Mars could be altered in such a way that it could sustain human and terrestrial life.
  • The impact of terraforming Mars would be that in the face of global calamity, there would be a place outside of our planet that would be a safe haven for mankind.
  • At this point, terraforming Mars is still a hypothetical idea.
  • Scientists believe that water and oxygen are available on Mars in a form that could be easily manipulated to be usable by human and terrestrial life.
  • Three major changes would have to occur for Mars to sustain life. These changes are: building up the pressure in the atmosphere, keeping it warm, and preventing the atmosphere from being lost to outer space.

Key Terms

  • Terraform: To transform the atmosphere or biosphere of another planet into one having the characteristics of Earth.
  • electrolysis: The chemical change produced by passing an electric current through a conducting solution or a molten salt.
  • Magnetosphere: The comet-shaped region around Earth or another planet in which charged particles are trapped or deflected. It is shaped by the solar wind and the planet’s magnetic field.

Terraforming Mars

The phrase “terraforming Mars” refers to the idea that the planet Mars could be altered in a way so that it could sustain human and terrestrial life. For a deeper understanding of the term, “terra” literally means land or Earth, so mankind would essentially be making (or forming) this land to be more like Earth.

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Terraformed Mars: This is an interpretation of what Mars might look like if it were terraformed.

Some people might question why exploring this hypothetical situation is important. The impact of terraforming Mars would be that in the face of global calamity, there would be a place outside of our planet that would be a safe haven for mankind. At this point, terraforming Mars is still a hypothetical idea.

The Process of Terraforming

For Mars to be suitable for human and terrestrial life, changes would be needed to be made to its climate, surface, and general properties. Although Mars is most like Earth out of all the planets in our solar system, it is still highly unsuitable for life as we know it. It is even thought that many years ago, Mars had a more suitable living environment with a thicker atmosphere and sufficient water to sustain life.

There are three major changes necessary for Mars to be suitable for life. The first change involves building up the atmosphere. This simply means that the surface pressure of Mars would need to be increased to sustain life. Currently, there is not a solution to this issue. Second, Mars would need to be kept warm. Scientists are focusing the least energy on solving this issue due to the amount of carbon dioxide on the planet. Carbon dioxide is a greenhouse gas which means that once the planet begins to heat, the excess carbon dioxide will probably help keep the heat near the ground. The last change that needs to be made is keeping the atmosphere from being lost to outer space. Solutions to this problem are not well-documented, but some scientists hypothesize that creating a magnetosphere would be helpful in resolving this issue.

It should be noted that water and oxygen supply are not listed in the necessary changes. Scientists have found that large amounts of water can be found below the Martian surface. It is currently mixed with dry ice (or frozen carbon dioxide), but it could be melted to be used as a water source. Additionally, it is hypothesized that through a process called electrolysis, scientists could separate the water molecules into oxygen and hydrogen to supply the planet with the necessary oxygen supply.

Europa’s Possible Ocean

Europa, one of Jupiter’s four moons, is covered by a layer of ice/water and scientists have multiple hypotheses to explain its structure.

Learning Objectives

Describe the evidence for oceans on Europa and the implications for life

Key Takeaways

Key Points

  • Europa is covered by a layer of liquid ice even though it maintains a constant temperature of around -145 degrees Celsius.
  • Europ, has tidal heating that develops from friction due to its eccentric orbit around Jupiter and its relationship with Jupiter’s other moons (known as Galilean moons).
  • It has also been proposed that volcanoes deep under the moon’s surface contain hydrothermal vents that heat and maintain the liquid water.
  • Scientists propose that Europa’s smooth surface, with very few craters, must be the result of ice covering an ocean which evens out the surface.
  • Geologists have analyzed images taken from the Voyager and Galileo expeditions and come up with two possible models for the surface of this moon, the thick-ice model and the thin-ice model. The thick-ice model is more widely held by scientists and has more evidence to support it.
  • The thick-ice model notes Europa’s craters and their surrounding concentric rings, which suggest the outer crust of ice would be about 6-19 miles thick and the liquid water underneath would be about 60 miles deep. The thin-ice model proposes that the icy crust would be about 660 ft thick.

Key Terms

  • Galileo: Galileo was an unmanned NASA spacecraft which studied the planet Jupiter and its moons.
  • eccentric: Not at or in the center; not perfectly circular.
  • Crater: A hemispherical pit created by the impact of a meteorite or other object.

Europa’s Possible Ocean

Europa, discovered in 1610 by Galileo Galilei, is one of Jupiter’s four moons (called the Galilean moons). Europa is covered by a layer of water/ice. It is fascinating to note that although Europa maintains a constant temperature of around -145 degrees Celsius, the water on its surface is not completely frozen (referred to as liquid water).

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Europa: An image of the Jovian moon Europa was acquired by Voyager 2

Europa’s Oceanic Properties

Europa has tidal heating that develops from friction due to its eccentric orbit around Jupiter. In other words, in a similar fashion to the tides flowing in and out on Earth due to the moon’s gravitational pull, the tides on Europa are affected due to its orbit around Jupiter and possibly also its orbital resonance with other Galilean moons. The planet ‘s gravitational pull is stronger on the near side than the far, creating tidal bulges that can crack the icy crust’s surface and heat the interior. It has also been proposed that volcanoes deep under the moon’s surface contain hydrothermal vents that heat and maintain the liquid water.

Evidence of an Ocean

Scientists propose the Europa’s smooth surface, with very few craters, must be the result of ice covering an ocean which evens out the surface. Originally there were hypotheses that the atmosphere burning up or weathering of the craters were the source of Europa’s smooth surface, but these ideas were discarded due to Europa’s thin atmosphere. Additionally, some parts of the moon’s surface shows blocks of ice that are separated but seem to fit together like a puzzle. These icebergs could have been shifted by slushy or liquid water beneath. Ridges in Europa’s landscape suggest existent water seeping up the ice cracks, refreezing, and then forming higher and higher ridges.

Models of Europa’s Surface

Geologists have analyzed images taken from the Voyager and Galileo expeditions and have come up with two possible models for the surface of this moon: the thick-ice model and the thin-ice model.

The thick-ice model refers to Europa’s large craters and their surrounding concentric rings. These rings are filled with what appears to be flat, fresh ice. Due to these observations and assumptions, combined with the calculated amount of heat present on the moon’s surface, the outer crust of solid ice would be about 6-19 miles thick and the liquid water underneath would be about 60 miles deep.

The thin-ice model, which is not widely supported by scientists, proposes that the icy crust would be only about 660 feet thick. Other scientists suggest that this layer is simply the outermost layer that changes constantly due to Europa’s tides. Currently, there is little evidence to support this model.