Mars is a pretty amazing place, and a shining example of this is a photo posted on NASA's Science Blog. The image won the Astronomical Photography of the Day award this week. The picture looks like a mountain … but there is a hole in it.
While it's not really the product of some weird mining experiment, the formation is indeed empty. What you're looking at is a lava skylight, a product of ancient volcanic activity beneath the surface of Mars.
This hole is located on the western slopes of a volcano called Pavonis Mons, the surrounding areas of which show some breathtaking geological features. There are long, wriggling lava tubes, fracture elements called grabens, and of course the large volcanic crater itself.
Volcano Pavonis Mons. (NASA / JPL-Caltech / Arizona State University)
The image above was taken by the Mars HiRise orbiter in 2011 and caught the attention of Mars explorers just because it was so unusual.
Upon closer inspection, it turned out that this is a hole in the surface, above the lava tube. It is hollow because sometimes lava flows can solidify on the surface while the flow is moving inside. The flowing lava can then flow out, leaving behind hollow caves – lava tubes.
Over time, the top can collapse, creating a gap.
Analysis of this hole showed that it is about 35 meters wide. The top of the rock that can be seen through the hole is at a depth of about 28 meters.
(NASA / JPL-Caltech / Arizona State University).
The digital terrain map allowed scientists to calculate the amount of material that fell out of the conical element; this in turn placed limits on how deep the pit could be. According to these calculations, the rock pile should be at least 62 meters high, which means that the pit itself should have been at least 90 meters deep before collapsing.
This is much more than any lava tube found on Earth.
Lava tube caverns like this one are very important because they may provide some protection from the radiation that hits Mars. This means that they can be good sites for building underground bases.
But there is also another meaning. If we're going to look for signs of life on Mars, caves might be the best option.
Lava tube on Earth. US Geological Survey
“Holes like these are of particular interest because their inner caves are relatively shielded from the harsh surface of Mars, making them relatively good candidates for the search for Martian life,” APOD explained.
“Therefore, these pits are prime targets for future spaceships, robots and even humans who will explore Mars in the future.”
Sources: Photo: NASA / JPL / University of Arizona, US Geological Survey
