Sarah Kaplan-Altman wants a stage magician to perform at her 8th birthday party. Teddy is bemused by the fact that his husband can literally do magic and their daughter just wants someone who fakes pulling a rabbit out of a hat. Billy doesn’t know what to think.
Ordinarily, planet hunters are looking for the telltale drops in brightness that happen when a planet crosses in front of its sun. That’s how we identify planets now — brief interruptions in the progress of light as it makes its way toward Earth. Not a presence, but an absence.
The rocks on Mars suggest it used to look like Earth. What happened?
For years now, scientists have been building a body of evidence that Mars looked very different in its distant past. There are features on the Martian surface that can only form in the presence of large bodies of water. Sarah Kaplan finds out more.
A vast shallow sea shimmered beneath oxygen-rich skies. The rocky crests of cliffs and hills reflected in the still water below. The landscape would have been familiar, except for its eerie desolation; nothing on the entire planet moved but the sands shifting in the wind.
This was Mars, circa maybe 4 billion years ago. Or at least, it’s one vision of Mars painted by Nina Lanza, a researcher at Los Alamos National Laboratory in New Mexico. In a study published last week in the journal Geophysical Research Letters, she and her colleagues argue that the discovery of manganese oxide (which forms in wet, oxygen-rich conditions) on the Martian surface suggests that the planet was once much more Earth-like.
Now, of course, Mars is a frozen, barren wasteland, covered in dull red rock that’s been bombarded and twisted into strange formations. Another study of the geology of Mars (also published last week in the journal Science) suggests that a particular kind of formation – a ripple in the sand that forms only in Mars’ current thin, arid atmosphere – can be found in fossilized form going back 3.7 billion years.
These two studies seem to bracket an important and confusing period in Mars’ history: the period when the planet started losing its atmosphere, and thus its ability to hold onto liquid water.
“Really the question again comes back to, ‘How fast did it get thin, when did it get thin, and why?'” said planetary scientist Christopher Edwards of the US Geological Survey. These studies “are placing a constraint on that, which is great.”