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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.
Unfortunately, we as humans cannot get to the Hellas impact structure. But, we have sent many robotic spacecrafts to Mars to study its surface in detail. Since the late 1960's, images and other data from National Aeronautics and Space Administration (NASA) spacecrafts that have orbited and landed on Mars have returned a wealth of information that have deepened our understanding of Martian geologic history and evolution. In this tour, orbital images of the surface, combined with other data such as digital elevation allows us to create perspective views as if we are hovering just above the Hellas region! But first, lets learn a little more about Hellas.
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.
Scientists who have studied surface features all around the Hellas region have shown that a variety of geologic processes have acted to modify the original surface of Hellas over time. These include impact craters that show exposed layered deposits (Milochau and Terby), volcanic flows and constructs along the inner and outer rim (Tyrrhena and Hadriaca Patera), large canyon systems (Dao, Niger, and Harmakhis Vallis), and kilometer-scale lobes of material that surround isolated hills and mountains (near Reull Vallis). So there's been a lot going on since Hellas was formed. We will be visiting some of these features close-up in this tour. So click on the tour button below and let's get started!