We can’t say with absolute certainty, but there are plenty of clues hinting to Mars having had quite an Earth-like appearance back in the day, with flowing water all around and an atmosphere to hold it all together. Now it’s dead, but probably not for long, if humans can do anything about it.
Despite the general consensus that water did exist at one point in liquid form on the surface of the Red Planet, there are not that many tell-tale signs left. In fact, the image you see here, say NASA and the University of Arizona, shows just one of few known places on the planet to present dune-like forms inside a channel, a clear sign of flowing water.
The image was taken back in 2016 with the HiRISE camera on board the Mars Reconnaissance Orbiter. The photo was shot from an altitude of 275 km (171 miles), and was only recently brought back into focus by scientists. It shows a small outflow channel of the so-called Lethe Vallis region, complete with what researchers describe as being a “teardrop-shaped island.”
To make sense of what you’re seeing, consider this: the round depression at the larger end of the island is an impact crater. Its location is pointed to where NASA speculates water once came from, with the tail end of the island pointing downstream.
So, the crater was created by a meteorite, while the island itself is the result of “extreme floods” in the region. Also in this image there are signs of lava flows (the edges of the channel), with the whole formation being the perfect blend of features created “by periglacial, volcanic, fluvial, impact, aeolian and mass wasting processes, all in one place.”
It also paints the picture of what must have been an incredibly dangerous place to be in billions of years ago.