Thanks to Linode for supporting this episode of SciShow News.

You can go to linode.com/scishow to learn more and get a $100 60-day credit on a new Linode account. [♪ INTRO] Mars is often thought to be a cold, dead hunk of rock. No liquid water, no geologic activity, and no life, unless you count that rover that sang itself Happy Birthday.

But over the past few years, we’ve realized that’s not entirely true. The red planet has quakes, and according to a paper published this week in Nature Astronomy, there might be molten rock churning beneath the Martian crust, too. On Earth, most of our volcanic and seismic activity happens where two tectonic plates smush up against each other, like the Ring of Fire that borders much of the Pacific Ocean.

But thanks to mantle plumes, hot columns of rock that bubble up from deep within the Earth, we can get volcanic and seismic activity in places like Hawaii, smack dab in the middle of that ocean. The volcanoes that form atop mantle plumes are known as hotspot volcanoes. And one of them, Mauna Loa, recently started erupting after a 38-year nap.

Meanwhile, over on Mars, the last last known volcanic eruption was somewhere between 53,000 and 210,000 years ago. Now, the heyday of Martian volcanism ended over three billion years ago, and for most of the time humans have been exploring Mars, we have thought of it as geologically dead. But in 2018, NASA’s InSight mission delivered a seismometer to the planet’s surface.

And at least in the region known as Elysium Planitia, the ground has spent the past four years quaking beneath InSight’s proverbial feet. But since Mars hasn’t displayed much evidence of tectonic plate activity, maybe mantle plumes are to blame. That’s where this new research comes in.

A group of scientists from the University of Arizona dove into a bunch of data that decades of previous research had collected. And based on all the evidence, the team argues there is only one explanation for all of the features in the area, including Elysium Planitia’s elevation compared to the surrounding lowlands, the strength of the gravity in that region, and the seismic patterns that InSight was recording. There’s an active mantle plume, bubbling up rock like a planet-sized lava lamp, and it’s hiding underneath a system of fissures called Cerberus Fossae.

These fissures were formed by past tectonic activity, and they just so happen to be the location of Mars’s most recent volcanic eruption all those millennia ago. So this claim isn’t completely out of the blue. However, more evidence is needed before anyone can say there definitely is an active mantle plume down there.

If we can find it, Mars will become the third place in the inner solar system that we know has active mantle plumes, after Earth and Venus. Or has at least one mantle plume. But that’s all Mars needs for us to learn that a planet we thought was completely dead has just really mellowed out in its old age.

Speaking of volcanoes, there’s another natural disaster in Mars news this week. According to research published last week in Scientific Reports, scientists may have found the source of an ancient megatsunami. Modern Mars might be a planet-wide desert, but scientists have suspected for decades that Past Mars was a completely different story.

In 1972, the Mariner 9 spacecraft spotted what looked to be ancient flood channels near the Martian equator. A long time ago, on the planet next door, Mars’s surface was partially covered in liquid water. So it made sense to send a lander there and do a bunch of follow-up science.

But when the Viking 1 lander arrived in 1976, it didn’t find the smooth landscapes scientists expected to see from all that flooding. Instead, the lander sent back photos of a whole bunch of boulders. At the time, scientists couldn’t figure out where these boulders came from, but in 2016, one team suggested that they were left behind by a megatsunami 3.4 billion years ago.

A big wave of water could certainly deposit a bunch of rocks from one part of Mars to another. But tsunamis don’t just happen. Something must have set it off.

The authors of that 2016 paper thought the most probable cause was an asteroid or comet impact. And that impact would leave behind a massive crater, even if it got worn down due to the ravages of time. Someone just needed to find it.

So some of those authors teamed up with some other scientists for a new study. After analyzing images of the planet’s surface near the original Viking 1 landing site, this team identified a crater 900 kilometers away that looked big enough to have been accompanied by a megatsunami. It’s called Pohl crater, named after a Science Fiction author.

It’s about 110 kilometers wide, and based on the location and neighboring rock layers, it appears to be just the right age, too. 3.4 billion years ago, this part of Mars is thought to have been covered by a big, deep ocean. The ideal location to trigger a massive tidal wave with an asteroid impact. So the team simulated different collisions to see what kind of impact could have not only formed Pohl crater, but also caused a megatsunami powerful enough to carry boulders to the Viking 1 landing site.

They found that the crater was likely formed by either a 9 kilometer asteroid hitting hard ground and encountering a lot of resistance, or a 3 kilometer asteroid crashing into more brittle ground. They determined that the second scenario was a better fit to the geologic record. And while both impacts caused tsunamis that could correctly restructure the coastal areas, a larger asteroid hitting stronger ground would have caused extra flooding beyond where the record suggests.

In the 3 kilometer, brittle ground simulation, the resulting wave would have been about 250 meters tall when it moved onto land. And if all this sounds vaguely familiar to you, that might be because this impact has a lot in common with a rather famous event on Earth. Around 66 million years ago, an asteroid crashed into the water just off the coast of the Yucatan peninsula.

It left behind a 110 kilometer wide crater roughly 200 meters below sea level, and caused a tsunami around 200 meters tall on land. And it also helped kill off the non-avian dinosaurs, which we don’t think were on Mars, so that’s a difference. But it’s possible that water the asteroid smashed into had evolved some kind of life.

Scientists will just have to keep up the search. And one day, maybe we’ll discover that the Mars of today is more than just geologically alive. Thank you to Linode for supporting this SciShow News video!

Linode is a cloud computing company from Akamai made for all levels of computer savvy users. Whether you’re working on a personal project or managing your enterprise’s infrastructure, Linode has the pricing, support, and scale you need to take your ideas to the next level. With Linode, you can easily scale resources up or down.

Use only what you need and only pay for what you use. Linode has been in the cloud computing game since 2003. Along the way, they’ve figured out the best balance of technology and price for your needs.

And Linode is giving you incentive to try it out: using the link in the description or linode.com/scishow, you get a $100 60-day credit on a new Linode account. Enjoy! [♪ OUTRO]