**Science Steering Group reports**

At the meeting on June 30-July 2, 2004, MEPAG heard reports on three
SSGs, two of which have completed and submitted their reports and one of
which is in process. MEPAG was singularly impressed with the quality and
depth of the analysis carried out by each of the SSGs, the more so in
that many of the questions addressed by them were originally ill-posed
or ill-defined. One important conclusion that we would like to highlight
is that these SSGs are an outstanding way to involve the science
community in providing scientific input that feeds into the programmatic
decisions that are to be made; there is no effective substitute or
alternative.

-   [Organic Contaminants SSG]{.underline}. This is an important report,
    because it represents some first steps by MEPAG to specify how the
    science community would like to see contamination requirements
    framed, as well as initial findings regarding quantitative limits on
    different classes of contaminants. In addition, this report contains
    an important discussion of the protocols necessary to distinguish
    contaminants from natural signal in life-related
    experiments---having effective strategies in this area will be
    important in designing both in situ and sample return missions in
    the future.

-   [Astrobiological Field Laboratory SSG]{.underline}. MEPAG's 2002
    Pathways SSG recommended that a major in-situ astrobiology mission,
    which was given the tentative name AFL, be considered for the next
    decade. The AFL SSG was asked to follow this up by analyzing what
    AFL could be. The study began with a valuable program-level analysis
    of the strategic planning issues associated with achieving MEPAG
    Goal I (life detection), and with an analysis of the projected state
    of the astrobiological exploration of Mars 10 years from now. This
    analysis will set the context for all Mars missions of the next
    10-20 years. From there, the AFL SSG presented an analysis of some
    possible in situ missions that could make a meaningful contribution
    to this overall exploration theme. Those descriptions elicited
    substantial discussion by the MEPAG audience, and further discussion
    in the future is anticipated. Finally, because there has been much
    recent confusion over terminology, the Mars Program has requested
    that the AFL SSG recommend to MEPAG a set of definitions related to
    Goal I. Definitions of "habitability", "habitat", "biosignature",
    and "life detection" were prepared, and have been accepted by MEPAG.

-   [Moon-Mars]{.underline} [SSG]{.underline}. The objective of this SSG
    was to define the scientific linkages between the Moon and Mars, and
    in particular, the activities that could be carried out at the Moon
    that would be of benefit to MEPAG's martian scientific objectives.
    The SSG has defined 20 primary linkages, which are organized into
    three categories: Scientific investigations, Resource-related
    issues, and Capability demonstrations. These linkages have been
    prioritized in a relative sense, and those priorities stirred up
    considerable discussion by the MEPAG audience. The SSG plans to take
    the feedback from those discussions, and to incorporate in a revised
    report.