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| An artist’s rendering of MSL landing on Mars. http://swri.org/4org/d15/planetsci/mars.htm One of the instruments whose primary goal it is to assess whether or not life once existed in sedimentary mounds on Mars is called SAM, which stands for Sample Analysis at Mars. SAM will search for preserved compounds that either indicate past biologic activity or are the essential precursors to life. To answer this question, SAM will first seek to understand the nature of the carbon compounds and other key elemental ingredients to life such as hydrogen, nitrogen, oxygen, phosphorus, and sulfur. These organic materials were initially deposited on both early Mars and early Earth by asteroids and comets at a rate over 1,000,000 kilograms per year. On Earth, an active biosphere reprocessed the original organics over the last four and a half billion years, but what happened to them on Mars? If life did indeed exist on Mars very early in its history, it is possible that the clues have been erased or reworked. It is also possible that SAM will discover organic compounds that have not been reworked by life, but instead by radiation and reactive surface complexes. The scientists on the SAM team certainly have their work cut out for them in piecing together this complicated puzzle. |
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The SAM instrument pre-launch.
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Another interesting question that SAM will be able to answer
is whether or not methane is being released on the surface of Mars today.
Methane is an important marker of biologic activity on Earth (think of cows)
and if it was discovered to be fluctuating on Mars, it could indicate activity
of living organisms. In 2003, a summer release of methane was reported to be
coming from a particular region on Mars. While this observation was a tricky
one to make using Earth-based telescopes, heavily questioned by the scientific
community, and still yet to be confirmed by another instrument, it has the
potential to have profound implications about life on Mars. SAM will be able to
measure even the tiniest amount of methane and monitor its changes over time.
The question of the existence and cycling of methane will be elucidated by SAM
as well as other important questions about the atmosphere and climate of our planetary neighbor.
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Graphic depicting methane concentration
during the 2003 northern summer on Mars observed release of methane. |
Geological evidence suggests that early Mars is a much
different than the vast, cold, dry desert we observe today. It had an active
hydrologic cycle, a protective magnetic field and thicker atmosphere. It was
probably warmer and maybe even had an ocean. Also, the last few decades of
astrobiological research have proven that life is capable of surviving in the
most “extreme” corners of the Earth. It is still possible that life developed
and thrived in this early Martian environment, and MSL will begin to probe for
clues that may show us earthlings that we have company.
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Image of the >3.4 billion year old Apex Chert, the first known body fossils found on Earth. Will we ever find something similar on Mars?
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