Geology Reference
In-Depth Information
Figure 8.15. Europa, showing key place names. The trailing hemisphere (centered on 270° W) is darker, partly as a result of implantation of
sodium- and sulfur-rich ions derived from volcanic eruptions on Io (from Spencer et al.,
2004
).
have been extensively modi
ed by tectonic processes,
including the formation of structural lineaments exceed-
ing 1000 km long, zones of crustal spreading and in
ll,
and the formation of terrain broken into zones of
upon liquid water, an energy source to support biological
processes, and the presence of the right chemistry (pri-
marily C, H, O, N, P, S, Fe, and various trace elements).
Europa meets these requirements, and, coupled with
the recognition that life on Earth exists even in extreme
environments, Europa is targeted for extensive future
exploration.
“
chaos.
”
Impact craters and cryovolcanic features are also seen.
Earth-based and spacecraft data show that non-ice
materials, such as magnesium salts, are present on the
surface, along with organic and sulfur compounds.
Surface materials are derived from three sources: (1) the
rocky interior, re
ecting the original compositions and
differentiated products related to the origin of Europa
(this material is brought to the surface by tectonic and
cryovolcanic processes); (2) materials carried to Europa
by comets, which would include organic compounds; and
(3) implantation of high-energy particles from Io.
Europa
'
s characteristics make it a high priority in the
search for life beyond Earth. Life as we know it depends
8.5.1 Impact features
Vo y a g e r images showed relatively few large impact cra-
ters on Europa, leading to the conclusion that it, like its
neighbor Io, has a geologically young surface and might
even experience active volcanism. The same calcula-
tions as led to the correct prediction of active volcanoes
on Io were also made for Europa. The results, however,
