THE SOLAR SYSTEM
Changes on Io in
close-up: three views of the
Pillan Patera region from
Galileo, taken in April 1997
(left), September 1997
(middle) and July 1999
(right). Between April and
September 1997 the volcano
Pillan erupted, producing the
dark deposit that can be sent
above right centre. By 1999
the red material from Pele (at
left centre) has started to
cover the dark material from
Pillan. It also appears that a
further volcano, to the right
of Pillan, has erupted since
the 1997 images. The
pictures cover an area
approximately 1650 km wide
and 1750 km high (1025 and
1090 miles). Europa, from Galileo.
False colour has been used
to enhance the visibility of
certain features in this
composite of three images
of Europa’s crust. It shows
what appear to be blocks
that have broken apart and
settled into new positions.
The icy plains, shown here
in bluish hues, subdivide
into units with different
albedos at infra-red
wavelengths, probably
because of differences in the
grain size of the ice. The
brown and reddish hues
represent regions where
contaminants are present
in the ice. The lines are
fractures or ridges in the
crust.
The composite was produced
by Galileo imaging team
scientists at the University
of Arizona. The images were
obtained during September
1996, December 1996 and
February 1997 from a
distance of 677,000 km
(417,489 miles).
It has been suggested that
beneath Europa’s icy crust
there may be an ocean of
liquid water, perhaps even
containing life. However,
there is no proof that an
ocean exists, and the
discovery of life there
would indeed be surprising.C Atl of Univ Phil'03stp 2/4/03 3:10 pm Page 105