Satellite imaging is becoming more and more important in helping us understand the dynamics of our world and even other worlds in our solar system. Mars, in particular, has come into focus, and its history is getting written one analyzed satellite image at a time.

In a new image captured by ESA’s Mars Express, two craters are seen close to each other on the surface of the red planet, but they are of very different origins, which adds to the complex history of the world.

The northern crater is a meteor impact, about thirty kilometers wide. An asteroid or a comet hit the surface, breaking through several layers of rock. The floor of the crater is fractured, and the remains of liquid ejecta can be seen around the edge of the crater. The fact that the ejecta show evidence of being somewhat liquid at the time, while the crater is relatively small, means that there was likely water or ice saturating the ground at the location.

On top of that, there is an outflow channel that can also be seen to the northwest of the crater. That means water burst through the crater wall to form channel islands and terraces along the banks.

Now, I mentioned that there are two craters in this image, and the second one is interesting in a different way. That crater was caused by a caldera and can be seen cutting down into the gentle rise of an old shield volcano. This particular Martian volcano is named Jovis Tholus, and it’s much smaller than the more well know Olympus Mons.

But there are actually a series of caldera craters that move from the peak of the volcano down to the southwest, where the youngest and largest breaks through the outer edge of the volcano. That means we’re not seeing the original edge of the volcano because the lava would have spread all around it, covering that original relief. While it was probably much higher above the surface before the calderas collapsed and flooded the plains, the volcano only stands about 1 km above those plains.

The striking difference between the two formations is even more obvious when looked at in a color-coded topographic image, which we will also include in our show notes. There, you can see that the impact crater is definitely below the surface, while the volcano rises above it. And another interesting feature is revealed – the slight bulge of another, less developed volcano to the east of the visible one. There’s even a small fissure vent in the center, such as we find in Hawai’i or Iceland here on Earth.

Mars was once an incredibly active planet, bombarded with larger meteors and erupting from volcanoes. Those eruptions would likely have moved water from underground aquifers to the surface through all the various faults that volcanoes tend to create, giving the water easy access to an unfortunately light atmosphere that couldn’t hold the water in. We think.

Again, the water situation on Mars is still a bit murky, but every image helps us get closer to understanding the past and present of this red world.

More Information

ESA press release