Is There Life Outside the Earth?
Exploring the Surface of Jupiter’s Moon Europa

The question of the possible existence of life outside the Earth is currently an active area of investigation for planetary scientists and astronomers.  Astronomers are confident that we will eventually be able to detect Earth-like planets around other stars.  If such observations reveal the presence of both oxygen and methane (as are found in Earth’s atmosphere), then that will provide strong evidence for the presence of life, because the nonequilibrum coexistence of these gases requires the presence of active production processes, most notably, metabolism.

    The atmospheres of the planets and moons of our solar system do not show any evidence of nonequilibrium chemistry, but nonetheless there are locations that could possibly provide the environmental conditions necessary for the continued presence of life.  Foremost among the candidates are the planet Mars and Jupiter’s moon Europa.  In this talk we will focus solely on Europa.

    Before we can think about setting off to explore Europa, we must first think about what life is, and what it does.  A review of some recent work provides some surprising insights.  For instance, nature makes use of carbon as the key element of biochemistry for the excellent reason that no other element can provide as great a diversity of chemical structures (polymers, DNA) and interactions.  Thus if life exists elsewhere, it is highly likely that it will be carbon-based.  This simplifies our problem.

    Europa may have a subsurface ocean of liquid water beneath its icy crust, and it is possible that some form of life may have found a way to survive and thrive there.  Images of Europa reveal surfaces that appear to have resulted from upwellings of warm materials from below.  Thus it may be that evidence of the presence of life may be found on the present-day surface of Europa.  NASA is planning a major mission to the Jupiter system for launch sometime around the year 2015, and a lander for Europa is being considered.  We will zoom in on Europa, using images obtained during the Galileo Mission, to assess the difficulties of landing and carrying out scientific investigations on the surface of this enigmatic moon.  

    The research described in this publication was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.