Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Science 1 December 1995:
Vol. 270. no. 5241, pp. 1460 - 1464
DOI: 10.1126/science.270.5241.1460
Prev | Table of Contents | Next

Articles

Venus Reconsidered

William M. Kaula

The Magellan imagery shows that Venus has a crater abundance equivalent to a surface age of 300 million to 500 million years and a crater distribution close to random. Hence, the tectonics of Venus must be quiescent compared to those of Earth in the last few 100 million years. The main debate is whether the decline in tectonic activity on Venus is closer to monotonic or episodic, with enhanced tectonism and volcanism yet to come. The former hypothesis implies that 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; some chemical evidence, particularly 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 million to 500 million years ago. The nature of the convective instabilities that caused the decline, and their propagation, are unclear.


The author is in the Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095, USA.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
An alternative Venus.
W. B. Hamilton (2007)
Geological Society of America Special Papers 430, 879-911
   Abstract »    Full Text »    PDF »


To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)