Astrobiology is the study of the origin, evolution, distribution, and future of life in the Universe. This field includes the search for habitable environments in our solar system and beyond, the search for evidence of prebiotic chemistry and life on Mars and other worlds, laboratory and field research into the origins and early evolution of life on Earth, and studies of the potential for life to adapt to challenges on Earth and in space. These topics require a multidisciplinary approach, bringing together experts in astronomy and astrophysics, Earth and planetary sciences, microbiology and evolutionary biology, cosmochemistry, and other relevant disciplines.
Although Venus, the Earth, and Mars are similar to one another, they have evolved in highly distinct ways. We now know that Mars once had water on its surface, and there are tantalizing hints that Venus might have too. Yet only the Earth is currently known to be habitable. Missions currently in operation, development and planning will greatly increase our knowledge of the forces driving planetary habitability and evolution.
Venus' extremely high surface temperatures and lack of water make it an unlikely place for life; current missions focus on Mars as a potentially habitable world.
Today, Mars is a cold world, roughly half as wide as Earth, with no oceans or liquid water at the surface. With its cold temperatures and thin atmosphere, liquid water cannot exist for long on the surface. In the past, conditions on Mars may have been more suitable for liquid water. In fact, surface feature seen from orbit have suggested that Mars may have had floods, bodies of water and even oceans in the past. If liquid water was once present on Mars, then environments that were habitable for life as we know it may have also persisted.
Questions surrounding the potential for current life on Mars also still remain. Evidence of methane in Mars' atmosphere, possible outflows of recent water, and data that hints at subsurface water reservoirs have peaked scientific curiosity in recent years. If any liquid water exists on Mars, particularly below the surface where it might be more stable, then habitats for life could theoretically exist today.
Because Mars bears some similarities to Earth, it is also an important target for validating models of potentially habitable, extrasolar planets. Data from Venus, Earth, and Mars is helping astrobiologists determine how to identify habitable worlds throughout the Universe based on the observations we can make using modern telescopes. Atmospheric models of the inner planets of our solar system can be used to understand the range of planetary conditions.
The potential for past or present life on Mars is a major driver of NASA research -- many of the studies performed in extreme environments on Earth are geared toward understanding how life can survive in harsh environment akin to those that may have existed on Mars.
By examining evidence of hydrated minerals and morphology of materials that have interacted with liquid water, Mars Science Laboratory will quantitatively assess the habitability through time of the landing site in Gale Crater. The mission is a critical step towards determining if Mars once supported life.
The giant planets of the outer solar system -- Jupiter, Saturn, Uranus, and Neptune -- and their rings and moons provide exciting opportunities in the search for habitable environments. There is particular interest in Saturn's moon Enceladus and Jupiter's moon Europa. Both are ice-covered and there is significant evidence for an ocean or oceans of water beneath the crust.
Europa is currently one of the top possible locations for life to exist outside of the Earth. It is thought to have an iron core, a rocky mantle and a surface ocean of salty water. Unlike on Earth, however, this ocean is deep enough to cover the whole surface of Europa, and being far from the sun, the ocean surface is globally frozen over. Heat generated from Jupiter's massive gravitational tidal forces causes the ocean to remain liquid and drives geological activity similar to plate tectonics. While Europa hasn't been studied closely since the Galileo mission, several future missions have been proposed to study this fascinating moon.
Enceladus has fissures, plains, corrugated terrain and other crustal deformations, and few craters. All of this indicates that the interior of the moon may be liquid today, even though it should have been frozen eons ago. Enceladus' surface is believed to be geologically "young," possibly less than 100 million years old. The Cassini mission observed icy plumes erupting from this moon's south polar region; measurements indicate that it was made of water and other gasses, and additional chemicals in the plume included simple and complex hydrocarbons such as propane, ethane, and acetylene -- further raising the potential for life beneath the surface!
Mars Science Laboratory Curiosity Rover
Modified from http://astrobiology.nasa.gov/missions/current/mars-science-laboratory/
Mars Science Laboratory (MSL) is the latest mission in NASA's long line of Mars explorers, and will help scientist determine whether or not past or present life could have gained a foothold on Mars. MSL is larger than any previous Mars surface mission -- five times larger than Spirit or Opportunity, and is built to carry larger instruments and to travel farther.
Components of MSL's instruments have been tested in Mars-analog environments on Earth, joining astrobiologists on field expeditions to extreme environments like Arctic islands, isolated deserts and barren Antarctic valleys. The ten instrument packages were designed with the objective to explore and quantitatively assess potential habitats for life on Mars, both past or present.
Orbital missions at Mars have provided a great deal of information concerning the mineralogy and geology of Mars -- hinting at regions where liquid water may have once flowed at the surface. MSL will help examine evidence of past water at the ground level, and will characterize the nature of current and ancient martian environments. MSL will help astrobiologists validate hypotheses of early martian environmental evolution and climate history. This will allow us to determine regions on Mars that could contain the best preserved environmental signals, or even biosignatures.
The environment of Mars has changed throughout the planet's history, and astrobiologists believe that Mars may have been habitable for life as we know it in the past. Even if life does not exist on Mars today, the rocks, soils and subsurface of Mars may preserve records of these ancient, habitable environments. One of the prime goals of MSL is to hunt for environmental signals and possible biosignatures that will help astrobiologists determine if Mars was once habitable for life.
The Origin of Life
Guiding Principles for Understanding Origin of Life
Two Ways to Investigate Origin of Life
Change in Ribosome after Origin of Life
Evolution of Ribosome before Origin of Life
Questions and Answers
What is Life:
Water and Organics on Mars:
Goldilocks and the 3000 Planets
The Antropocene Era
Questions and Answers