Jacob Samorodin wrote:
Seismographs have been succcessfully landed on Mars by the Viking-2 spacecraft. The results, I understand, were disappointing.
But seismographs could play an important roll in unraveling a
martian mystery...

Alex writes:
Actually, both Viking Landers carried a *seismometer*, not a seismograph. Though the distinction is frequently lost on non-geoscientists, a seismometer is the term for any instrument used for the detection of geophysical motion; a seismograph is the recording device attached to the seismometer. As you alluded, the device carried on Viking 1 Lander failed to uncage and was not available to network with the successfully deployed seismometer on Viking 2 Lander during the entire duration of mission.

Jacob Samorodin wrote:
Dr. Blackwell?
It occurs to me, that since Malin & Co. have released those startling MGS images, last year, showing what appeared to be 'recent' debris aprons and erosion channels on the sides of steep martian terrain, that are theorized to be the result of lateral liquid water eruptions, such "violent events" may result in a seismic signal that could be picked up by an extremely sensitive seismograph, even one located
hundreds of kilometers away...That's assuming these "events" still
occur on a fairly regular basis.

Alex writes:
In theory, a seepage outburst of the type Malin and Edgett reported could be detected by a single (or preferably a network array) of seismometers deployed on the Martian surface, provided of course that the background noise is at a level to detect such an event. Fron a practical standpoint, however, even though some of the seepage sites are geologically young, one has to assume that these are rare events and any such seismological detection would be completely serendipitous. Nevertheless, if a good candidate signal is detected and triangulated, then a high-resolution imager could attempt to image any surficial changes at the location, though, needless to say, this is a VERY optimistic view based on past history - but not out of the question.

Fortunately, the problem of tying seismological data to martian subsurface water can be attacked from another direction. Future seismometers (e.g. those to be deployed by the four CNES-supplied NetLanders in 2007) will use both passive and active seismometry to *image* the martian subsurface for stratigraphic interfaces between soil, rock, and putative water, which can be detected due to its dielectric an d long-wavelenght scattering properties. If water (either solid or liquid) is detected at depths that are consistent with the layer depths associated with the seepage sites this would be strong evidence supporting the water-based model(s) for their existence.

Alex R. Blackwell
University of Hawaii

Alex R. Blackwell
University of Hawaii