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Over the last few decades, we’ve found evidence that various places in the solar system, like Mars or Saturn’s moon Enceladus, could be or could have once been habitable. But life on our Moon is a different story.

The Moon is a generally dry, irradiated wasteland, and it has been for billions of years. Of course nothing’s absolutely sure in science, but we’re as confident as can be that today’s Moon is lifeless. But a new paper published online last week in the journal Astrobiology says that it might not have always been that way.

For a cosmic blink of an eye, just as life here was starting, it also could have survived on the Moon. The problem with living on the Moon is that there are lots of problems. Depending on the temperature, any liquid water immediately either freezes or boils away to interplanetary space, because there’s effectively no atmosphere to keep liquids, liquid.

And speaking of the temperature, days can be up to 127°C, while nights are about 300° colder. No atmosphere or magnetic field also means there’s nothing to block destructive solar radiation from raining down on the surface. There are some impressively hearty microbes, to be sure, but the Moon is a thoroughly difficult place to live.

It probably wasn’t always like this, though. By collecting research from a huge range of disciplines, a pair of astrobiologists found that we’ve developed a picture of the very early Moon that, at times, seems downright habitable. The first time was when the Moon formed about four and a half billion years ago.

As its rocks coalesced, they released huge amounts of heat and trapped gases. The second time was around half a billion years later, when another burst of lunar volcanic activity released more heat and gas. Both times, the gases could have stuck around for tens of millions of years, possibly forming an atmosphere thicker than the one around Mars today and allowing for liquid water on the surface.

And the Moon had a magnetic field back then, too, caused by moving molten rock deep beneath the surface, which would have helped block some of the most dangerous incoming radiation. The paper’s authors also point out that all this was happening just as life was gaining a foothold down here on Earth. And even if scientists are right that the Moon’s improved conditions wouldn’t have lasted for very long, we already know that life here didn’t take long to get going.

Some microbes could have even been blasted off Earth by asteroid impacts, only to land on the Moon and start things up there. Or the other way around. Of course, this isn’t proof that there was ever life on the Moon; but it certainly does give us a new view of our sweet little satellite.

Thankfully, life on Earth is much more stable. And a lot of that is because the Sun is usually pretty chill. I mean, there’s the occasional solar storm, but most days, the Sun just sort of sits there, warming your face and maintaining life.

Except, it hasn’t always been so peaceful. In this week’s issue of Nature Astronomy, scientists studying some of the oldest rocks in the solar system report that when it was young, the Sun acted out a lot more. Which, didn’t we all?

It’s hard to find physical records from the very early solar system, because there wasn’t really anything here yet. So these days, a lot of our knowledge comes from a combination of well-tested models, observations of young stars, and more indirect evidence like the locations of planets. We can also study tiny, ancient grains of rock buried within meteorites, but learning their secrets can be tricky business.

For example, it can be hard to tell if elements in the grains have been there for billions of years, or if they formed through more recent radioactive decay. Together those methods do a fantastic job teaching us about our early environment. But scientists always want to get closer to the source.

And this week, a team of physicists reported that by studying gases trapped within ancient minerals, they’ve found direct evidence of some of the Sun’s earliest temper tantrums. Or, as they’re called in the paper, “a phase of intense irradiation not recorded by minerals that formed later.” Whichever works. The team studied a type of deposit known as CAIs, short for calcium-aluminum-rich inclusions, which are found in all sorts of meteorites.

Specifically, they focused on those found inside a meteorite that fell on Australia in 1969. That sample was full of hibonite crystals, a type of mineral, and likely formed more than 4.5 billion years ago. The CAIs are less than a tenth of a millimeter across, but those tiny grains were some of the first things to form in our solar system.

And they’re great records of our star’s activity. When the newly formed Sun gave off bursts of high-energy particles like protons, some protons would crash into atoms in the CAIs and break them into smaller pieces, stuff like helium and neon. And by studying those elements trapped in the rock, we can get a clearer picture of what the Sun was up to.

But that still happens today, so just measuring helium and neon wasn’t enough to learn something about the young Sun. So instead, the team had to compare the CAIs to the rest of the meteorite, which was younger rock, to get an idea of what happened when. And once they did, they could confidently say that the Sun was much more actively releasing particles early in its life.

This pretty much matches what those other methods have taught us about stellar evolution:. Young stars are active and belchy, then they bit more. get older, maybe get a job, settle down a bit more. But this is the first time we’ve seen direct evidence of that early activity using such ancient rocks.

And it gives us one more way of understanding how we all got here in the first place. It’s a good thing the Sun settled down, though, because it makes life on Earth a whole lot easier. And hey, maybe it helped the Moon out once or twice, too.

Thanks for watching this episode of SciShow Space News! If you would like to keep up with the latest research happening in astronomy and planetary science, you can go to youtube.com/scishowspace and subscribe. [ ♪ Outro ].