2010 Annual Research Report

Hartmann's PSI research is generally in the area refining techniques for using the populations of impact craters to interpret the age, geologic processes, and geologic history of formations in which the crater form.  This is supported by a new MDAP grant that started in 2010.  He has also been active in the area of reviewing the evidence for a solar-system-wide cataclysm 3.9 Gy ago, in which he has given talks suggesting that the evidence is not as strong or consistent as is thought by most people in the field.

The crater related work was focused on material assembled during past and 2010 workshops at the International Space Science Institute in Bern, Switzerland.  A new series of workshops was approved by ISSI and started in fall, 2010.  The new team includes Olga Popova (Russia, team co-leader with Hartmann), Cathy Quantin (France), Stephanie Werner (Norway), Ernst Hauber (Germany), and Hartmann.  The primary new project aims at measuring the “production” size-frequency-distribution (PSFD) of the smallest visible craters on Mars (diameter D ~ 2m to 20m) using HiRISE imagery of selected young areas of Mars.  The PSFD is the size distribution before removal of small craters by erosion, infill, etc.  As shown by the earlier ISSI team (Popova et al., MAPS, 2003) it is affected by loss of weak meteoroids in the Martian atmosphere.   In order to understand the shape of the curve at the small sizes, scientists also measure on other imagery at crater sizes D up to several hundred m or more,  in order to understand trends and ages as determined from the larger craters.   Our fall, 2010 workshop at ISSI concentrated on measuring the SFD in several regions, but concentrated on an area of very young shield volcanoes in Tharsis, discovered by team member Ernst Hauber.

Note that the production rate of new Martian craters has been measured by Malin et al. in 2006 from MOC images.  Thus, once we fully understand the production size distribution in the D range from 2 m to 50m or so, we have a powerful geological tool not only for measuring surface ages on small young features, but also on detecting geological processes causing loses of the smallest craters, as revealed by distortions and depressions of the SFD curve measured surfaces where erosion or infill has obliterated the smallest craters.

In another project, Hartmann continued work on a paper started about 3 years ago on a 60 km crater east of Hellas, at 38⁰ S latitude.  This crater is notable for containing an array of different , striking features that give diagnostic clues about accumulation and flow of ice-rich materials on Mars.  The new paper has coauthors Dan Berman (PSI) and Veronique Ansan (University Nantes, France) and possibly others.  The north wall of the crater contains lobate tongue-shaped features resembling glacial flows, which Hartmann discussed earlier (Hartmann, Thorsteinsson, Sigurdsson 2003, Icarus); these show distal arcuate ridges matching those found at the distal foot of Martian gullies. 

Hartmann is also operating in partial retirement mode, and on my own time I have continued research on historical and other projects.