Jim Klemaszewski - Water on Europa
[NOTE: The link beneath each image will take you to the Planetary Photojournal page where you can download the image, and which also contains the original caption.]
Europa, about the same size as Io and the Earth's Moon, has an outer shell composed of water ice that has been modified by geologic activity for most if not all of its history
The faulted and fractured surface of Ganymede, the icy Galilean satellite larger than the
Although Callisto is nearly the size of Ganymede, its surface does not reveal evidence of
The surfaces of the icy satellites Callisto, Ganymede and Europa display amounts of geologic
These dark bands are younger than the surrounding icy plains, and formed when the icy surface fractured with subsequent rotation of the icy plates over a subsurface that was able to flow. However, it cannot be determined from these images whether that movement occurred rapidly over a subsurface that was liquid water or slowly over warm ice that deformed and flowed over hundreds to thousands (or millions) of years. One of these wedge-shaped bands was imaged at higher resolution on the third orbit.
The trajectory of Galileo's second orbit of Jupiter provided global-resolution of Europa's trailing hemisphere (centered at longitude 270) which was previously imaged by Voyager at very low resolution.
This global view of Europa (left = true color; right = false color) shows that mottled terrain has a geographic
distribution that is broadly equatorial. The equatorial presence of mottled terrain, and its absence near the poles probably indicates that the ice at Europa's poles is relatively thicker and therefore more resistant to
mottled terrain formation. This global image was also used to refine imaging targets on the fourth and sixth orbits. On the fourth orbit the dark circular spot on the lower left side of Europa was imaged, as well as
The surface of Europa at high resolution is seen to consist of numerous criss-crossing ridges that range in nature from simple and double ridges to complex parallel ridges. In some locations these ridges are disrupted by subsequent geologic activity
One feature that was met with enthusiasm is a smooth circular area about 10 km (6 miles)
Although this feature may represent the extrusion (eruption) of water or slush onto the surface, it may also have originated from localized heating of near-surface materials. In either event, this feature is a surficial expression of internal, near-surface heat. An additional observation on the fourth orbit included a dark circular feature. This feature is an impact crater that is interpreted to have penetrated Europa's icy shell.
The sixth orbit provided the strongest evidence for a subsurface ocean. The dark area
The disruptive activity broke the crust into blocks with a range of sizes, some up to ~6
This terrain on Europa produced by subsurface heating and disruption is referred to as "chaos terrain", because of its resemblance to chaos terrain on Mars where subsurface water appears to have erupted onto
the surface at the head of many outflow channels. Chaos terrain has now been identified in many areas on Europa, some of which are nearly 100,000 square kilometers in extent, indicating widespread heating and
disruption of Europa's crust.
This image shows that the plains, which appeared "smooth" at lower resolutions, consist of numerous criss-crossing ridges. Scientists (and students) can use the principle of cross-cutting relationships to
determine the relative ages of the ridges: The youngest ridges are on top and cross-cut the older ridges below. This principle can be used to determine if the orientation of ridges on Europa has changed with time.
(Question: how has the size of ridges changed with time in this region?)
was imaged on the 6th orbit, and then again on the 12th orbit. The data from these orbits
http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA01175The principle behind this is based on how we (people) see depth -- we have two eyes that
or any 3-D image, is produced by taking two pictures of the same feature from two different
all point to a consistent story that Europa most likely had a subsurface ocean at the time these features formed. The big question is whether or not that ocean is still present today.
If it is, there could be up to twice as much liquid water on Europa compared to Earth's oceans. That's a lot of water. And with all that water, scientists are wondering if life might be present in Europa's ocean. How are we going to find out? NASA is planning on sending another spacecraft to go into orbit around Europa. This spacecraft will take pictures of the entire surface, but will also use radar to try to penetrate the ice shell to determine its thickness and whether or not an ocean is there today. If that mission is successful, then a lander will be sent to Europa that will have the ability to melt through the ice and launch a small robotic submersible into this alien ocean. And some of today's students -- not just those who excel in math and science, but also artists, writers, and business majors -- will be the explorers of tomorrow.
|[Home] [Program ] [Registration] [FAQ] [Graduate Credit] [Archive]|
Funded by NASA/JPL Earth Science Flight Projects