Previous: The Biggest Volcano in the Solar System
Next: Could There Be Planets Beyond Neptune?



View count:123,255
Last sync:2019-06-13 13:00
Mars might be full of salty liquid water! Plus, a guide to the upcoming Lyrids meteor shower.

Hosted by: Hank Green
Dooblydoo thanks to the following Patreon supporters -- we couldn't make SciShow without them! Shout outs go to Justin Lentz, John Szymakowski, Ruben Galvao, and Peso255.
Like SciShow? Want to help support us, and also get things to put on your walls, cover your torso and hold your liquids? Check out our awesome products over at DFTBA Records:

Or help support us by becoming our patron on Patreon:
Looking for SciShow elsewhere on the internet?

(SciShow Space Intro plays)

Hank: For a planet that looks like a desert, Mars sure has a lot of water.  Of course, it's all frozen in the glaciers and polar ice caps or trapped as wisps of vapor in Mars' thin atmosphere, or at least that's what we thought.  According to a new study of data from our old friend the Curiosity Rover, there may be salty liquid water all over the planet, hidden just below the surface.

Normally, the low air pressure on Mars means that even when the temperature is above 0 degrees, water doesn't sit around in liquid form, it just goes straight from ice into vapor.  But there is a way for ice to become liquid even if the temperature and pressure don't normally allow it: salt, which can change a water's melting point, which is why scientists were so excited when, in 2008, the Phoenix Lander found high levels of Perchlorate in Martian soil near the polar caps.  

When there's enough humidity, Perchlorates can bond with water to form Perchlorate Hydrate.  Eventually, these compounds can absorb enough moisture to dissolve, creating some very salty water or brine.  Back in '08, researchers studying the data from Phoenix figured that at more than 60 degrees latitude from the equator, the humidity on Mars was high enough for Perchlorate to form brine, at least for a few hours every day in the Martian spring.  

But the scientists weren't sure if that meant Perchlorate would show up everywhere in that region.  Having liquid water a couple hours a day in certain places is cool, but it's not exactly an ocean or even a pond.  Then, Curiosity found Perchlorates near the Martian equator at Gale Crater.  Now, Curiosity isn't set up to detect brine directly, but a team of researchers from Denmark used Curiosity's humidity and temperature data, collected over two years, to model the climate at Gale and see if brine could form there, too, and they found that it could.  Deeper than 15 cm below the surface, it's relatively cold and the humidity never reaches 0, so the researchers predict that there is always brine down there.  Within 5cm of the surface, conditions are a little less stable, and during the day, it's often too warm for water to stay liquid, but the team thinks brine could form on the surface of Mars and just below it for a few hours every night, and if liquid water can form near the equator, the driest, hottest part of Mars, it can probably form elsewhere on the Martian surface where conditions are more favorable.  

Now this is the part where I bum you out and tell you that 15cm below the surface of Mars where they think there could always be salty water, temperatures are too low to support life as we know it.  So don't get your hopes up that there's some Martian weird little glumpy life things swimming around down there, and then there's the bummer that Perchlorate is also super corrosive, it gets into the cracks in our equipment, it reacts with metal, creating all kinds of structural and electrical problems, plus it's harmful to humans because it interferes with thyroid function.  So we might want to take that into account next time we send equipment or people over to our next door planet.

But take heart, because there's a great show going on in the sky next week.  The Lyrids meteor shower will peak during the mornings of April 22nd and 23rd, and even though the Northern hemisphere will be the best place to see it, the Northern half of the Southern hemisphere should have a good view, too.  Meteor showers happen when Earth passes through the debris left by a comet, which burns up in the atmosphere to create those tell-tale flashes of light.  In the case of the Lyrids, they'll be traveling through the path of the comet Thatcher, which orbits the sun every 415 years.  This shower is called the Lyrids because the meteors streak from a central radian point in the constellation Lyra.  But since the dust-like particles don't actually light up until they're relatively far from that point, meteors can appear anywhere in the sky.  Meteors will be easiest to spot after midnight, when the radiant point will be above the horizon, and since the waxing crescent moon will have already set, the sky should be dark enough to spot 10 to 20 meteors per hour.  The next showers are the Eta Aquarids and Delta Aquarids in May and July, but light from the moon will make them harder to see.  Your next good opportunity won't be until the Perseids meteor shower in August.  So if you live in the right part of the world, and you have the opportunity, you might wanna catch this one, all you have to do is find a dark spot, maybe a friend, sit back, and wait.  
Thanks for joining me for SciShow Space News, especially to our patrons on Patreon.  If you want to be one of those people who helps us explore the universe, you can go to to learn how you can help out and get a bunch of cool rewards in the process.

(SciShow Space Outro plays)