alcaray wrote:
if the RADAR on Express will pass over this feature (I recall they won't get full coverage of the planet because of their orbit)?

Alex writes:
"Full coverage," assuming of course you mean full global coverage, depends on the particular Mars Express instrument you are talking about. Some instruments, for example HRSC, will not be able to give global coverage because, to some extent, they sacrifice areal coverage to spatial resolution. MARSIS, which operates at very long wavelengths and has a larger spatial footprint (both downtrack and crosstrack) will be able to collect data at greater altitudes as it proceeds to and from periapsis. From the MARSIS page on the Mars Express website:

"The best ground penetrating studies are made during night when the Martian ionosphere is least active and when the spacecraft is less than 800 km from the Martian surface, a condition that occurs for 26 minutes during each 6.75 hour orbit. During the lifetime of the mission, the instrument will be able to conduct ground penetrating studies over the entire planet.

alcaray wrote:
Also, assuming it does, will it have sufficient resolution to display features of the "circular structure" that are covered with softer material?

Alex writes:
It all depends on the dielectric properties of the "circular structure" and whether its subsurface expression falls within MARSIS' optimal sensing parameters (i.e., does not lie in the near-surface "blind zone").

Alex R. Blackwell
University of Hawaii