Physics
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003agufm.p11b1045m&link_type=abstract
American Geophysical Union, Fall Meeting 2003, abstract #P11B-1045
Physics
5420 Impact Phenomena (Includes Cratering), 5475 Tectonics (8149), 6295 Venus
Scientific paper
The Venus Magellan mission in the early 1990's provided radar imagery that mapped numerous impact craters, randomly distributed over the planet's surface. Analysis of these images shows that the majority of the craters remain in pristine condition, but about 25% have been modified by tectonism and/or embayment. Fully 23% of the modified craters are located in the Beta-Atla-Themis (BAT) region, just 1/6th the planetary surface. Furthermore, 61% of the craters unambiguously both tectonized and embayed concentrate in this region, together with the planetary geoid highs and profuse volcanism. The process of impact cratering has been well studied; we use their modification to assess the tectonic and volcanic activity of the BAT region. In our study we correlated Magellan radar images and topographic data to analyze the tilting for both modified and unmodified craters. We use stereo-imaging for those few craters with multiple Magellan cycle coverage to achieve higher topographic resolution. In addition, the construction of basic maps clarified the degree of modification of these features. For example, the 102.2 km diameter crater Bonheur, located on the east side of Beta-Phoebe chasma, has been heavily tectonized and tilts towards the rift. Meanwhile, the pristine crater Isabella, 176.0 km diameter, tilts away from Atla. This pattern may indicate the nature of tectonic activity of both areas. Although both Beta and Atla regiones have approximately similar crater density, the distribution of modified craters differs. Atla contains a higher concentration of modified craters (33%) than Beta (23%), and the modified craters on Beta are randomly distributed unlike those on Atla. On Atla, four of the unambiguously tectonized and embayed craters cluster near the geoid high, but embayed-only craters are minimal and tectonized-only craters become more common at lower elevations. Significantly, craters with dark parabolic halos are thought to be among the most recent 10% of features on the planet. Uvayasi, a parabola-associated crater near the peak of Atla, has been both tectonized and embayed which dates the activity here as very recent. However, no such parabolic craters occur near Beta.
Jurdy Donna M.
Matias A.
Stoddard Paul R.
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