|
SUMMARY
|
|
Chyba: Jupiter's moons have subsurface
oceans.
Farmer: Life's building blocks may come
from space.
Jakosky: Understanding of life's origin
has changed.
|
|
Icy Europa
Europa's crust is made up of blocks which are thought to have broken apart
and "rafted" into new positions. These features indicate that
Europa, a moon of Jupiter, may have once had a subsurface ocean. Other
evidence hints that the ocean is likely still there.
Learn More
IMAGE:
NASA/GALILEO
|
 Europa has a core of iron and nickel (shown
in gray) surrounded by a rock shell (brown), and a layer of water in ice or
liquid form (blue and white). The surface layer is shown as white. IMAGE: NASA
|
Recent Europa News:
Jupiter's
Deadly Radiation Could Power Life On Europa
Europa's
Bowed Cracks Could Point To Global Ocean
|
Q: What's the most
surprising thing we know about the possibility of extraterrestrial life that we
did not know 30 years ago?
Chyba: We've learned so much in the past 30
years! But there are two big surprises: It is starting to look like most big
icy worlds (Jupiter's moons Europa, Ganymede, Callisto) have subsurface oceans;
and we've learned about the extent of the Earth's deep subsurface biosphere.
Farmer: I think the most surprising thing we have learned is that
there is a lot of complex prebiotic carbon chemistry going on out there in
interstellar space, enhancing the broad availability of basic building blocks
needed for life. Then it may become simply a question of environmental
opportunity.
Because we have discovered
that microbial life can exist just about anywhere there is liquid water, this
may largely be determined by the availability of that unique compound. We have
been discovering that liquid water may be much more common elsewhere in our
solar system than previously thought. (E.g. Mars, Europa and other icy
satellites; perhaps even within the interiors of large asteroids.)
Finally, the discovery of
extrasolar planets around other stars in our galaxy certainly has to rate up
there as well.
Jakosky: I would say that the biggest shift is in the last 20 years,
rather than 30. Twenty years ago, after the Viking missions to Mars, the
consensus was that there was only one planet in our solar system that could
support life -- the Earth. However, our understanding of terrestrial biology
and the history of life on Earth has changed dramatically.
We now understand that life
originated very quickly after it became possible on Earth, that life is much
more diverse and robust than we had thought (and able to occupy niches that
were thought uninhabitable), and that life may even have originated in the
types of extreme environments that we will find on other planets. These really
have opened up the possibility that life could exist elsewhere in our solar
system, and there are as many as a half-dozen planets or satellites on which we
think life might exist.
Next Page: What are the odds of ET?
advertisement
advertisement
