As part of a wealth of new information presented on Thursday by the MESSENGER science team, the image above shows the mountainous rim of the 160 mile (257 km)-wide Raditladi impact basin on Mercury. (View the full image here.)
Areas seen as mere bright spots in previous lower-resolution images have been revisited by the orbiting MESSENGER spacecraft, which revealed them to be unexpectedly unique and bizarre landforms.
Named “hollows”, these irregularly-shaped rimless depressions have bright, slightly blue-tinted interiors and often occur in clusters. Hollows have since been identified in many areas across Mercury but the exact process that creates them still remains unknown.
Some scientists speculate that they may be the result of erosion by solar radiation. Mercury, being as close to the sun as it is and lacking a proportionally-protective magnetic field like Earth’s, is constantly scoured by the solar wind. Volatile materials in Mercury’s crust, exposed by meteorite impact, may be literally sandblasted away by the sun!
The lack of craters within these hollow regions seems to indicate that they are relatively young features. In fact, they may be an active process that continues to this day.
“Analysis of the images and estimates of the rate at which the hollows may be growing led to the conclusion that they could be actively forming today,” says David Blewett, a staff scientist at the Johns Hopkins University Applied Physics Laboratory (APL). “The old conventional wisdom was that ‘Mercury is just like the moon.’ But from its vantage point in orbit, MESSENGER is showing us that Mercury is radically different from the moon in just about every way we can measure.”
MESSENGER’s first six months around Mercury sure have been very productive ones! It will be interesting to see what else will be discovered by the only spacecraft ever to enter orbit around the first rock from the sun.
Read more about this and other recently-announced findings from MESSENGER here.
Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington