Future Venus Missions Options

[Phil Stooke]

Oh well, might as well start that new topic since it's already well advanced in the Juno area...

My perspective on landers is as follows. All the landers we've had so far were dropped blind onto an essentially unknown surface. Any future landers can be targeted for specific terrains. It really is not true that we have had representative landings. Even a descent image or two, a panoramic photo plus a bit of surface composition, from a simple Venera-class lander just updated a bit, would be useful if we could put several down at well chosen targets. My choices would be:

Examples of the main plains units (smooth, fractured, ridged)

tesserae

high elevation radar-bright tesserae

large fresh lava flow unit ('fluctus')

crater dark parabola

crater ejecta outflow unit

dunes area.

And I have always assumed, rightly or wrongly, that it would be relatively easy to put these down, so they ought to be fairly inexpensive as planetary landers go.

Phil

[edstrick]

The frustration of understanding anything about the geology of the Venera Lander sites is the utter lack of geologic context for the surface panoramas. Three "DIMES" type images, taken at 1, 5 and 20 (for example) kilometers with a 45 degree field of view, from my perspective, is almost mandatory for any understanding of the geologic context of chemical/minerological measurements from a lander.

It's lack -- we've only approximately located the landing sites of Venera 8, 9 and 10, 13 and 14, and Vega 1 and 2 -- in providing real geologic context has led to essential uncertainty on what geology some of those landers are on. Some are just not well located in regions of complex geology, Venera 8 in particular.

Radar data, by it's inherent nature, tells a lot about surface materials physical configuration: relief, roughness, texture, internal scattering, etc, but almost nothing about chemistry. In addition, it's remarkably hard at times to relate to visible geology. Witness the difficulty in relating optical observations of the Huygens landnig site to radar data. Shuttle radar penetrates a meter or so under sand sheets in the Sahara and show geology underneath you can't see standing there or in visible imagery from orbit. On a mission dominated by geochemistry-science, I'd prefer 3 good descent images over spiffy surface panoramas any time, much as I love a good pan!