Exobiology in the Solar System & The Search for Life on Mars - ESA

SCIENTIFIC METHOD AND REQUIREMENTS
<strong>The</strong> advent of new, lightweight, technology has made it possible to produce small
highly <strong>in</strong>tegrated experiments which can be placed <strong>in</strong> many positions on landers and
rovers. It is, however, essential that <strong>the</strong>se systems <strong>for</strong>m an <strong>in</strong>tegrated package.
Achievement of <strong>the</strong> scientific objectives with<strong>in</strong> a low mass can only be achieved if
<strong>the</strong> objectives are focussed and <strong>the</strong> concept <strong>for</strong> <strong>the</strong> means by which <strong>the</strong> objectives are
to be achieved are clear and straight<strong>for</strong>ward. Here we discuss <strong>the</strong> scientific methods
available and <strong>the</strong>ir requirements.
II.6.8.1 Objectives
Initially, a panoramic survey of <strong>the</strong> site must be obta<strong>in</strong>ed. This survey must:
– identify <strong>the</strong> position of <strong>the</strong> land<strong>in</strong>g site;
– provide an assessment of <strong>the</strong> rock density at <strong>the</strong> site;
– determ<strong>in</strong>e <strong>the</strong> rock distribution and its heterogeneity;
– determ<strong>in</strong>e <strong>the</strong> rock-size distribution and assess evidence <strong>for</strong> bimodal distributions
caused by different processes;
– study <strong>the</strong> evidence <strong>for</strong> macroscopic <strong>in</strong>fluence on <strong>the</strong> site (flood<strong>in</strong>g, impact, etc);
– <strong>in</strong>vestigate aeolian effects (such as w<strong>in</strong>d tails and ventifacts) and allow comparisons
with global circulation models;
– study <strong>the</strong> surface photometric function;
– <strong>in</strong>vestigate <strong>the</strong> bulk m<strong>in</strong>eralogy of rocks and soils;
– search <strong>for</strong> spectral <strong>in</strong>homogeneity of soils and compare this to <strong>the</strong> local
morphology;
– search <strong>for</strong> spectral <strong>in</strong>homogeneity of rocks and <strong>in</strong>vestigate evidence <strong>for</strong> sedimentation
and <strong>in</strong>-flux of external material;
– search <strong>for</strong> potential targets <strong>for</strong> <strong>the</strong> rover, <strong>in</strong>clud<strong>in</strong>g identification of unusual
morphology, differentiation between wea<strong>the</strong>red and unwea<strong>the</strong>red rock, study of
significant colour differences, identification of potential dangers to navigation.
Assum<strong>in</strong>g that some <strong>for</strong>m of mobile device (such as a rover) is deployed, <strong>the</strong> survey
must also:
– assess <strong>the</strong> morphology of disturbed soil and determ<strong>in</strong>e its consistency;
– compare <strong>the</strong> colour of rover tracks with undisturbed soil and assess <strong>the</strong> compaction
parameters needed to produce this colour change;
– assess <strong>the</strong> rate at which <strong>the</strong> disturbed soil re-equilibrates with <strong>the</strong> surround<strong>in</strong>gs.
In addition, <strong>the</strong> survey must make:
– an assessment of <strong>the</strong> damage to <strong>the</strong> site caused by <strong>the</strong> land<strong>in</strong>g (<strong>in</strong>clud<strong>in</strong>g contam<strong>in</strong>ation
result<strong>in</strong>g from <strong>the</strong> land<strong>in</strong>g strategy employed);
– determ<strong>in</strong>e <strong>the</strong> orientation of <strong>the</strong> land<strong>in</strong>g vehicle;
– determ<strong>in</strong>e <strong>the</strong> optical depth at <strong>the</strong> site <strong>for</strong> purposes of power management.
<strong>The</strong> system must also determ<strong>in</strong>e <strong>the</strong> properties of <strong>the</strong> diffuse illum<strong>in</strong>ation. <strong>The</strong> sky
can be extremely bright and very red because of <strong>the</strong> high optical depths of atmospheric
dust (Thomas et al., 1998). In order to provide a quantitative assessment of <strong>the</strong>
colour and albedo of <strong>the</strong> surface, <strong>the</strong> properties of <strong>the</strong> airborne dust must be measured.
It should be noted that <strong>the</strong> spectra, derived from Mars Pathf<strong>in</strong>der imager measurements,
showed little or no contrast <strong>in</strong> <strong>the</strong> 800 nm - 1 µm range. This spectral region
was specifically targeted to <strong>in</strong>vestigate absorption by Fe 2+ -bear<strong>in</strong>g m<strong>in</strong>erals. <strong>The</strong> only
soil with any significant absorption (near <strong>the</strong> rock ‘Lamb’) showed a band of