The Magellan imagery shows that Venus has a crater abundance equivalent to a surface age of 300-500 Ma and a crater distribution close to random. Hence the tectonics of Venus must be quiescent compared to Earth's in the last few 100 Ma. The main debate is whether its decline is closer to monotonic or episodic, with enhanced tectonism and volcanism yet to come. The former hypothesis implies most radioactive heat sources have been differentiated upward; the latter, that they have remained at depth. The low level of activity in the last few 100 million years inferred from imagery favors the monotonic hypothesis; the low abundance of radiogenic argon favors the episodic. A problem for both hypotheses is the rapid decline of thermal and tectonic activity some 300 to 500 Ma. The nature of the convective instabilities that caused the decline, and their propagation, are unclear.
Lunar and Planetary Science Conference
- Pub Date:
- March 1996
- EVOLUTION: THERMAL;