Mars looms large in the scientific imagination, as well as in fiction. Of all the worlds of the solar system, it’s the only one Earth-like enough for exploration with Earth-like tools: Its atmosphere is thin and transparent, its surface is dry and cold, and it’s close enough for regular study. From telescope eyepieces, we’ve probed the Red Planet for centuries. And over the past 50 years, we’ve even sent instruments for a closer look.
However, in geological terms, that’s just a sliver of time. Mars’s deep history remains a mystery.
“A major issue that we have pretty much in all of Mars studies is that we just don’t know what was going on in the distant past,” said planetary scientist Eryn Cangi of the University of Colorado Boulder.
Scientists have found volcanoes, dried lake beds, and other signs that the planet once looked very different, but many mysteries about why and how it changed remain unsolved. Here are five linked tangles scientists have yet to unravel.
