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We might be able to use slime molds to help predict the shape of matter in the universe, and the Rosetta mission may have figured out why many comets seem to be missing a bunch of nitrogen.

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[♪ INTRO].

One of the best ways to solve problems in science can be, well, borrowing from other kinds of science—because there are often surprising connections between disciplines that seem totally unrelated. Sometimes, though, these connections can go from unrelated to like, far-fetched.

Like, that can't be a thing! Like, say, slime molds predicting the shape of matter in the universe. And yet, in a paper published last week in the Astrophysical Journal Letters, a team of researchers claim their model based on slime mold is so far our best predictor of the distribution of matter in the universe.

The team was trying to predict the shape of the cosmic web, the thread-like network of matter that spreads through the whole universe. It hasn't always looked the way it does today—and understanding how the cosmic web has evolved over time is key to understanding the forces driving its structure. Go back to just after the Big Bang, and stuff was spread pretty much uniformly throughout space.

Then, gravity started to take over. Areas with a little extra density began to pull other material in— so denser areas got even denser and less-dense areas emptied out until a net-like structure formed. At dense spots where strands intersected, clumps of matter eventually collapsed into the first galaxies, loosely connected by tendrils of gas and dust called the intergalactic medium.

Because their stars give off light, astronomers today can map the locations of the galaxies pretty easily. But uncovering the web has proven to be harder—at least, until we got a little help from Physarum polycephalum, a slime mold. P. polycephalum is basically just one big cell, but for a single cell, it is surprisingly complex.

It has a bunch of nuclei but no brain, yet it can form memories, learn, and even pass on that knowledge to other slime molds. Most important for the team of astronomers, though, is how it moves. When searching for food, the slime mold sends out bits of itself in all directions.

If one part finds a source of food, it flourishes and the whole organism kind of grows in that direction. And that's not all that different from how clusters of matter grow, if you imagine that anything with gravity is like a source of food for the cosmic web. In fact, a postdoc at UC Santa Cruz realized that, mathematically, the evolution of the cosmic web was pretty similar to the growth of slime mold.

So, to apply this technique to the cosmic web, the team took a computer model for slime mold growth and modified it for the three-dimensional nature of space. Then, they marked the present-day locations of galaxies as food sources and let the mold grow. The result was basically a map of possible connections between galaxies near and far.

The stronger the link, the thicker the web. To check their results, the team compared these predictions with hundreds of observations made by the Hubble Space Telescope. And it worked!

Where the slime mold model said there should be gas, there was gas. Where it said there should be a lot of gas, they found that, too. So does this mean that slime molds and galaxies are actually connected and that we're all just the same thing?

No. Not exactly. But it does mean that living things often use pretty efficient techniques to solve problems, whether they know it or not.

And it shows us that a brainless organism can help us tackle one of the most complex problems in cosmology. Closer to home, scientists from Europe's Rosetta mission might have solved another mystery recently: why many comets seem to be missing a bunch of nitrogen. Nitrogen is one of the most abundant elements in the universe, yet when scientists study comets, they find around ten times less than they expect.

In a paper published in the journal Nature Astronomy back in January,. Rosetta scientists explain why that might be. Between 2014 and 2016, the Rosetta spacecraft studied.

Comet 67P/Churyumov-Gerasimenko up close. Along with lots of other stuff, it measured the comet's absorption spectrum, the wavelengths of the Sun's light that are absorbed instead of bouncing off the surface. Every substance absorbs light in a unique pattern, so gaps in the reflected spectrum help scientists identify the materials on the surface.

There was one gap in the infrared, though, that they couldn't identify. And it wasn't just in one spot, but seemed to be all over the comet. The problem was, identifying unknown spectral features is tricky business, because things like temperature, pressure, and even crystal shape can affect the exact position of a gap.

So it's not always straightforward to match a given gap to a specific molecule. And, of course, there's a nearly-infinite supply of potential molecules, so pinpointing the mystery molecule basically came down to guess-and-check in the lab. To do a guess-and-check on Rosetta's observations, researchers had to simulate the frigid surface of a comet deep in the vacuum of space.

Once conditions were right, the team used an instrument similar to the one onboard the spacecraft to make a spectrum and look for that mysterious gap. After some experimentation, the researchers found a possible match: salts made from the molecule ammonium. Rosetta had previously detected these nitrogen-based molecules in dust particles ejected from the comet's surface, but now it seems like they might be nearly everywhere.

That could mean a lot of nitrogen that wasn't being counted before is actually locked up in ammonium salts, which could go a long way toward settling the mystery of comets' missing nitrogen. And if comets really are rich with nitrogen, that opens up an exciting possibility: maybe comets like 67P helped deliver the ingredients of the air that we are breathing right now. Slime molds might still be this week's MVP in space news, but if comets did deliver the nitrogen in our air, we owe them a lot of credit as well.

Thanks for watching this episode of SciShow Space News! While you are here, I want to tell you about our SciShow pin of the month. Every month, we here at SciShow design a new, space-themed pin, and our March pin is of Pioneer 4!

It was the first spacecraft from the U. S. to escape the Earth's gravity and enter orbit around the Sun, and the pin was designed by one of our amazing animators here at SciShow. You can only get it this month, so if you're interested, check it out at or in the description below.

And also, that helps support the show. [♪ OUTRO].