The comet Sliding Spring whizzed past the Red Planet last week at a speed of over 203,000 km/h, coming as close as 140,000 km—a proximity that is not only very rare for comets, but never before seen for Mars.
Not only has this allowed NASA’s Hubble Space Telescope to take some extraordinary composite images for us to gawk at (composite, because a single exposure would be problematic given the objects’ respective brightnesses (Mars is 10,000 times brighter than the comet), and their simultaneous motions), but it has also given scientists a once in a lifetime opportunity to study the comet without having to go to it. The rovers positioned on Mars were able to take pictures of the comet’s core, which could shed light on the beginnings of our solar system. Sliding Spring was formed at the same time of our solar system’s creation, thus making it a time capsule of sorts, revealing details about the conditions of the early solar system. This is an especially unique opportunity, given that this is Sliding Spring’s first journey from the Oort Cloud into the inner solar system, thus meaning it has never been heated by the Sun, and most likely looks very similar to how it did 4.6 billion years ago.