Okay, let’s be honest: We have found a lot of water on Mars.

The planet has vast underground ice deposits, enough polar ice for a global flood, and maybe even some sort of liquid water flowing every now and then. By now, no one really doubts that Mars used to be wet, and that ancient water is still trapped in or on the planet.

What they do argue about is whether future astronauts would be able to use that water, or whether it’s too inaccessible or dirty to even try. But according to a paper in last week’s issue of the journal Science, at least some places on Mars have gigantic drinkable glaciers sitting just below the surface. So get your space pickaxes ready.

When we hear someone say there’s ice beneath Mars’s surface, it’s easy to imagine buried glaciers of pure frozen water. But that’s not always what scientists mean. Many of them have traditionally pictured Mars’s ice closer to a sort of concrete, with ice crystals mixed with dust grains and rock fragments.

Still, it’s been hard to tell if that’s right because so much of the ice is underneath layers of dust and rock. We know it’s there because of indirect measurements, but those measurements don’t tell us tons about how mixed it is with the surrounding rocks. So in this new study, the authors looked for a more direct way of understanding Mars’s ice: Pictures.

They used photos from the Mars Reconnaissance Orbiter to investigate eight hills where erosion has revealed what’s beneath the surface dust -- sort of like seeing the layers of rock in the Grand Canyon. Each hill had a layer of pretty much pure ice -- with hardly any rocks or dust mixed in -- sitting within a couple meters of the surface layers. The scientists found the ice by looking at enhanced-color images, since everything on Mars is tinted red with dust.

And in those images, the hillside ice practically glowed blue like a glacier on Earth. The team also confirmed it was ice using other methods, like measuring what sorts of electromagnetic radiation it gave off. And they found that the ice layers were tens or even a hundred meters thick.

Those ice reserves could be vital sources of drinking water of course for future astronauts. But by splitting water molecules into hydrogen and oxygen, the ice could also help produce breathable air, too. But the ice sheets didn’t just appear on Mars.

Models show that they probably came from gigantic snowstorms millions of years ago. So like on Earth, future scientists could also drill into these ice layers and learn how the Martian climate has changed over time. And that could answer some surviving questions about why the Red Planet is so dry.

Still, before we can even think about using that water, we should probably figure out how to safely send people to Mars. Baby steps. Besides looking at Mars, astronomers have also been working on a much larger mystery: why galaxies give off so much light.

Specifically, certain wavelengths of infrared light. They’ve known about this for years, but they’ve had trouble identifying the culprit. See, no one molecule or small group of molecules seemed to exactly match the observations.

But another paper in the same issue of Science has helped zero in on where all that extra light is coming from. With this study, the authors were trying to confirm a previously proposed idea: that the glow wasn’t just from one or a few molecules, but a huge class of them. This class is called polycyclic aromatic hydrocarbons, or PAHs.

These are rings of carbon atoms surrounded by nothing but hydrogen. There are over a hundred different PAHs, and the larger ones tend to emit similar kinds of infrared light when they move around in empty space. So it’s possible that the glow astronomers saw from galaxies could be the combined light of dozens of distinct but similar PAHs.

But no one has ever conclusively seen one of these molecules in outer space, and scientists weren’t sure how they’d form. Also, their light blends together so well that it’s hard to tell if any one specific molecule is actually out there. That’s where this new study comes in.

Instead of looking for individual PAHs, the researchers used radio telescopes to search for light given off by precursor molecules that can easily react to form them. These molecules are sometimes known as PA(N)Hs, where the “N” stands for a nitrogen atom where there would be a hydrogen in a true PAH. The additional nitrogen makes these molecules sort of off-balance, so they rotate and vibrate more distinctly than a lot of the symmetrical molecules do.

And that makes them give off more light. To search for these molecules, the researchers looked at the Taurus Molecular Cloud, a cloud of gas and dust about 400 light-years away. There, they found one of these building blocks, known as benzonitrile.

It isn’t a big molecule -- it only has thirteen atoms -- but it is important, and finding it in outer space means we must be on the right track. Benzonitrile reacts easily with other molecules to produce exactly the kinds of PAHs that could make galaxies glow in infrared. So it could explain how the PAHs ended up in space in the first place.

Now, there’s still some way to go before this mystery is completely solved. For one, we’d like to actually identify a PAH in space. And there’s still some uncertainty about where these precursor molecules, like benzonitrile, would come from.

But now, we’re at least more confident that all those steps are somewhere on the ladder. We just need to fill in the details. Thanks for watching this episode of SciShow Space News!

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