ESA Exobiology
Introduction
ESA's life sciences activities cover every aspect of space life sciences, including biology, physiology, biotechnology, biomedical applications, biological life-support systems, exobiology, animal research and access to ground facilities. They have included exobiology research since 1992, when the Exobiology and Radiation Assembly (ERA) flew on the Eureca mission. This approach continues with the Biopan facility on the Russian Foton missions. Four missions flew in 1992, 1994, 1997 and 1999, and the next is planned for October. In addition, EXPOSE will be installed no earlier than 2007 on the external payload site of Columbus aboard the International Space Station, mounted on a device to point the experiments towards the Sun. These facilities are helping to understand the survivability and damage/repair mechanisms of organics, microorganisms and invertebrates in space conditions.
ESA Astrobiology Science Team Study
As a logical progression from exobiology research in low Earth
orbit, an Astrobiology Science Team was created to survey current
research in exobiology and then formulate recommendations for a future
search for life in the Solar System. (The full findings are published
in ESA SP-1231.)
The main recommendation was that Mars should be
ESA's prime target. Three fundamental requirements were identified for
a search for life on Mars:
- the landing site must have high
astrobiology potential. That has not been the case so far. Sites with
sedimentary deposits and relatively free from wind-blown sand are prime
targets;
- samples must be taken in several locations, free
from surface oxidation. A rover is needed, with a drill to reach well
into the soil and surface rocks, and a system to prepare the samples
for analysis;
- integrated measurements must be performed on the
site and samples. An astrobiology package should carry: a microscope
for general examination of the samples at a resolution of 3 µm (plus a
close-up camera with 50 µm resolution); an infrared Raman spectroscope
for identifying mineral and organic molecules, with near-IR excitation
for biological and geochemical studies; an alpha-proton-X-ray
spectrometer for identifying chemical elements; a Mossbauer
spectrometer for measuring iron composition and oxidation states; a
pyrolitic gas chromatograph and mass spectrometer for isotopic,
elemental, organic and inorganic molecular composition, and chirality
measurements; sensors for hydrogen peroxide and other oxidants.
Two parallel studies on the Exobiology Package were then carried out
by Kayser-Threde (D) and Officine Galileo (I). A 15-month Phase-A/B
study will begin in mid-2002. Recently, ESA commissioned a study by the
Babakin Space Centre (BSC) to see if Russia could provide a low-cost
mission to deploy the Exobiology Package. Also considered was
cooperation in view of the Russian experience in inflatable reentry and
Mars rover technologies. The main findings were that the mission is
feasible with Russian technologies, using the Soyuz-FG or Dnepr
rockets, that the Exobiology Package could be accommodated on a 120 kg
rover, and that the Inflatable Braking Device could be used. The study
focused on missions in the 2007 and 2009 Mars launch windows. In early
2002, ESA's Concurrent Design Facility confirmed the technical
feasibility, although the 2009 slot is more realistic. Further studies
are planned.
Future Activity
For the longer term, the Astrobiology Science Team highlighted other areas:
Europa and other bodies possibly having subsurface water and internal heat sources are candidates for both extant and extinct life.
Titan
has an atmosphere of nitrogen and methane, together with a great number
of trace hydrocarbons, nitriles and oxygen compounds. Surface deposits
of hydrocarbons have been predicted, although water ice is now
considered to be dominant. Interest lies in the study of fundamental
physical and chemical interactions driving planetary organic chemistry,
and in the possible development of a life system in the absence of
liquid water but with other liquids.
Meteorites
are samples of solar debris and of the material ejected from bodies
such as Mars and the Moon. Martian meteorites are being closely studied
for evidence of extinct life. A sample of martian sedimentary material
would be a major breakthrough, likely to yield important information
about life on Mars.
Comets were probably an important source of organics for the primitive Earth and other planetary bodies.
Meteorites and Micrometeorites
imported major amounts of extraterrestrial organic material to the
Earth - perhaps 10^17 kg of carbon over the 300 million years of
the late bombardment phase. Improved collection of micrometeorites by
the Space Station and other vehicles is needed to allow unambiguous
analysis of the organic components.
Organic Molecules
are potential building blocks of pre-biological materials, but they may
suffer degradation and racemisation in space. The effects of space
conditions on organics such as amino acids, sugars, lipids and nucleic
acid bases must be studied. They may be protected by associating with
mineral dust particles found in micro-meteorites and comets. Similar
studies are also needed on polycyclic aromatic hydrocarbons (PAHs).
Experiments of this type require access to the external environ-ment of
a space station or other vehicle with dedicated facilities.
Microorganisms
subjected to the space environment, especially the UV radiation and
heavy-particle radiation flux, tend to be damaged progressively and
die. However, certain types can survive in space for long periods ,
especially if they are protected inside meteorites. Continuing space
experiments will improve our understanding of the underlying damage
processes, the survivability of a range of organisms, and the
possibility of life being spread around the Solar System by meteorites.
Laboratory Simulations can
provide valuable information on the organic chemistry processes in
comets, on interstellar grains and in meteorites. Simulation of
planetary environments and the study of their effects on microorganisms
have both fundamental and practical value. Laboratory Studies
will continue to provide the essential fundamental experiments in the
search to understand the earliest steps in the emergence of life. In
conjunction with field experiments, they will make important
contributions to the knowledge of how life develops and survives under
extreme conditions, including deep subterranean life, and its
application to the search for life elsewhere in the Solar System.