- About PSI
Impact craters, large and small, are common on all solar system bodies with a solid surface and one of our favorite planetary bodies to explore has been Mars. This tour focuses on one of it's most striking craters, Hellas Planitia.
Hellas is the largest well-preserved impact structure on Mars and spans more than 2000 kilometers across in the southern hemisphere, a region that is much more heavily cratered and higher in average elevation than the northern hemipshere. This region is often referred to as the "southern cratered highlands". The depth of Hellas from its bottom to its inner rim is more than 4 kilometers. To put this in perspective, the depth of the Grand Canyon in the United States is roughly 1 mile (1.6 kilometers), which means the depth of Hellas is about 2.5 times greater than the Grand Canyon! This is one deep hole! The western part of the Hellas basin contains the lowest point on Mars, about 8.2 kilometers below the Mars datum or Martian "sea level". The formation of the impact structure is believed to have taken place in the early Noachian epoch (click here for description of the Martian time scale), anywhere from 3.9 to 4.6 billion years ago. In the time since its formation, Hellas has been subject to infilling by eolian, fluvial, glacial, and volcanic materials.
Lets take a closer look at the Hellas region, the area highlighted by the black box in the image above.
Note some of the other features in the Hellas Planitia region. Hellespontes Montes is mountainous terrain on the western rim of Hellas. Alpheus Colles is a region with knobs or small hills on the floor of Hellas. Hellas Chaos is a region of broken terrain on the floor of Hellas. Malea Planum is an area of smooth plateau or plains along the southwestern rim of Hellas. Thus, different feature types have different names. To see a list of terms for various feature types on planetary bodies, click here. To see the history of how features get their names, click here.
Now, back to Hellas-- while we cannot walk around the impact structure to look for altered minerals, overturned layers, or other features close-up like we can at an impact crater on Earth, this does not mean we cannot study the Hellas region at all.