[♩INTRO].

In the last twenty-five years or so, astronomers have discovered thousands of planets orbiting other stars. And at this point, they have a pretty good idea what these planetary neighborhoods are like.

For example, they know we don't typically see planets similar to Neptune very close to their stars, probably because worlds like that would lose their atmospheres to the star's radiation. But, of course, there are some exceptions. At the end of April, researchers announced that they found a Neptune-like planet in the scorching region immediately surrounding its star.

Get out of there little planet! Go! Their news was published in the Monthly Notices of the Royal Astronomical Society, and figuring out how this object ended up there could help scientists understand how solar systems evolve.

The world is called NGTS-4b, but the researchers have given it an edgier nickname: “The Forbidden Planet.” It's about nine hundred light-years away, is smaller than Neptune, and has a mass of about twenty Earths, but it gets its nickname from its orbit. This planet is super close to its star, orbiting it every 1.3 days. And that puts it in an area astronomers call the “Neptunian Desert.” This is the region right around a star where scientists have only ever detected a handful of Neptune-like planets.

They aren't totally sure why these worlds are missing from these regions, especially because they can contain other kinds of planets, like hot Jupiters and super-Earths. But it may be that they lost their battles against their stars' intense radiation. Planets like Neptune have thick atmospheres, but when they get too close to their stars, the stellar radiation heats up those atmospheres, and they probably just drift into space.

This hypothesis is supported by the fact that astronomers have observed similar planets right at the edge of the Desert quickly losing their atmospheres. So it seems likely the situation could be even worse for objects closer in. So things don't look so good for the Forbidden Planet, which is about 20x closer to its star than Mercury is to the Sun.

But somehow, it's survived. Scientists are studying two main possibilities for how this happened. One is that the planet formed farther out and drifted inward after its star's most active period.

That would have allowed the planet to avoid a lot of the high-energy X-rays that would have heated its atmosphere. Alternatively, the planet could have been saved by having an especially massive core, which would have helped it keep a gravitational hold on its atmosphere. The case isn't closed, but scientists will keep looking into these possibilities.

And, they'll be on the lookout for other forbidden planets. Because understanding where these worlds live and how they got into their orbits can help us pin down models of solar system evolution. Much closer to home, other scientists have been having their own struggles with harsh planetary environments.

Except, their challenge is to figure out how people will breathe on Mars. Until now, humans have either taken their own supply of oxygen to space, or generated it from water molecules. But hauling around oxygen or water gets pretty heavy and expensive.

It would also be completely impractical for sustaining a future settlement on Mars, a planet whose atmosphere is mostly carbon dioxide. But last month in Nature Communications, a team of engineers announced they may have found a solution. And their inspiration came from an unlikely place: comets.

Comets are one of the few places in space where we see molecular oxygen, or O2. And for a couple of years, we've known about the strange chemical reaction that produces it. It begins when a comet heats up, and water molecules on its surface evaporate.

Then those molecules get picked up by streams of particles radiating off the Sun, and they slam back into the comet's surface. At high speeds, those tiny collisions are enough to rip oxygen atoms off other compounds on the comet and create O2. In the study published last month, the engineers wanted to figure out if this reaction could also happen with carbon dioxide.

After all, carbon dioxide has two oxygen atoms and is also found on comets. But honestly, this was more of a long shot, because carbon dioxide molecules form a straight line, with the oxygen atoms on opposite ends. It would take some impressive molecular acrobatics to get those two oxygens to join together.

But the researchers are good researchers and at least wanted to test the idea. So they created an experiment. In it, they slammed carbon dioxide into a piece of gold foil.

Since gold has no oxygen atoms, any oxygen produced would have had to come from the CO2. And sure enough, the collision created oxygen! That meant oxygen atoms were being torn off carbon dioxide, transforming it into molecular oxygen and plain carbon.

This is an extremely unusual kind of reaction — but it's also promising. Although the particular reactor used in this experiment only made one or two oxygen molecules for every hundred molecules of carbon dioxide, it proves that this type of chemistry is possible. Scientists are optimistic that this process could be scaled up and could eventually help give explorers a source of breathable air on Mars.

And if nothing else, they point out that we just learned something really cool with comets. Space research is constantly challenging us to look for the exceptions to the rule. From unexpected reactions and forbidden planets, we can learn a lot by studying the oddballs.

This episode of SciShow Space News is brought to you by our patrons on Patreon, including today's President of Space, who is no oddball, just an awesome guy, Matthew Brant. Thanks, Matthew! If you want to learn how to support SciShow and help us bring you more news like this, you can go to patreon.com/scishow.

And to our current patrons, thanks for everything you do. [♩OUTRO].