[meteorite-list] Features Of Early Martian Environment And Presence Of Water Drive Search For Life Forms

[Ron Baalke]

http://www.sciencedaily.com/releases/2009/04/090416125214.htm  

Features Of Early Martian Environment And Presence Of Water Drive
Search For Life Forms

ScienceDaily (Apr. 16, 2009) - Solar energy and winds, collisions with
asteroids and comets, and changing magnetic fields have all altered the
environment of Mars, a planet that may have been able to support life
during its history, as documented in a special collection of papers
published in the current issue of Astrobiology.

Compiled by Helmut Lammer, PhD, Senior Editor of Astrobiology, from the
Austrian Academy of Sciences, this special paper collection features a
report by Pham et al. that presents a semi-analytical model to evaluate
the influence of impacts on the evolution of the carbon dioxide-based
martian atmosphere. The results of this study indicate that impacts
alone cannot satisfactorily explain the loss of significant atmospheric
mass since the Late Noachian (~ 3.7 - 4 Ga).

In other words, if the martian atmosphere was much denser at about 4 Ga
than at present, impact erosion was most likely not responsible for the
removal of the atmosphere at that time. Terada et al. present a 3-D
model to assess the effects of exposure to solar energy and winds on ion
escape on early Mars 4.5 Ga, and to demonstrate how ion erosion could
have led to the loss of water that might have been present on Mars. Two
reports, by Horváth et al. and Fendrihan et al., explore the existence
and survival of two types of bacteria under martian surface and
environmental conditions, and the types of habitats that might have
existed to support these life forms.

"The results of Pham et al. and Terada et al. indicate that Mars should
have lost its denser initial CO2 atmosphere very early," says Dr.
Lammer, PhD, "and may have been cold and dry during most of its history.
Leblanc and colleagues propose a new concept in exploratory missions
with Mars Environment and Magnetic Orbiter (MEMO), which would gather
data to help scientists understand how the martian surface, atmosphere,
and magnetic field have evolved, and how those questions raised by
Terada et al. and Pham et al. can be investigated."

This Special Paper Collection is available free online at
http://www.liebertpub.com/ast