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  • {♫Intro♫}

  • Back in 2018, scientists found what seemed to be a massive lake deep under the ice near

  • Mars's south pole.

  • And that was pretty surprising, because even though there's plenty of evidence that water

  • used to flow across the surface, the chances of there still being liquid water seemed pretty slim.

  • For one, the pressure from Mars's atmosphere is so light that it would be impossible for

  • water to stay in a liquid state in most places. And then there's the fact that its surface

  • temperature averages about -63 degrees Celsius.

  • But an underground lake wasn't out of the question. And last week, a study published

  • in Nature Astronomy provided new evidence that this massive lake existsand that there

  • are smaller pools around it.

  • The study was based on data from the spacecraft Mars Express, which also made the 2018 discovery.

  • It's currently orbiting the Red Planet and bouncing radar off it to explore beneath the

  • surface. [NASA/JPL-Caltech]

  • How can a satellite measure what's under the ground? Well, I'll tell you...

  • Mars Express does this by sending down pulses of radio waves, which penetrate the crust

  • and bounce back in different ways depending on the material they travel through. So the

  • echo of these waves can help us tell the difference between water and rock, even if we can't see them.

  • In the latest study, scientists collected a bunch of this radar data and analyzed it

  • using a technique we use on Earth to look for liquid water below glaciers, in places

  • like Greenland and Antarctica.

  • It's an approach that's designed to distinguish pools of water from frozen or dry layers of the crust.

  • And sure enough, they found an underground lake right where they expected, about 20 by

  • 30 kilometers wide. But it wasn't alone! They also found evidence of other, smaller

  • bodies of water surrounding this lake.

  • The researchers still aren't sure why exactly these lakes exist.

  • They may have formed after some underground volcanic activity warmed up the area about

  • a million years ago.

  • And then, as the temperature dropped, natural salts dissolved in the water may have kept

  • it from freezing, just like road salt keeps water from becoming ice.

  • Thanks to all that salt, this water isn't likely to sustain future human explorers,

  • but it gives us a new place to look for current or past life.

  • In other space news, astronomers have gotten one step closer to solving a mystery about

  • the Sun that's been eluding us for decades.

  • Since the 1940s, scientists have known that the Sun's corona, or atmosphere, is around

  • a million degrees Celsius. But its surface is only around 6000 degrees. [Luc Viatour]

  • And that's pretty confusing. Because normally the farther away you are from a hot thing,

  • the less hot it is. That's how thermodynamics works.

  • So some process has to be heating the corona, and scientists aren't sure what it is.

  • But last week, in another paper published in Nature Astronomy, scientists revealed that

  • they may have found an important clue.

  • They were using data collected by three separate solar observatories, including NASA's IRIS

  • spacecraft, which has a high-resolution camera tracking the movement of matter and energy

  • through the Sun's lower atmosphere.

  • Back in 2014, that camera was able to capture the first clear look at thin, bright explosions

  • of light known as nanojets.

  • Scientists believe these form from nanoflares, which are arcs of plasma and magnetic field

  • lineslike miniature solar flares. They form when the Sun's tangled magnetic field

  • lines break and reconnect thanks to the movement of charged particles.

  • Normally, nanojets are hard to spot against the bright Sun, but in 2014 there was what's

  • called a coronal rain event.

  • That's when a bunch of cool plasma flows from the corona down to the surface of the

  • Sun in what kind of looks like a waterfall.

  • Except like, made of plasma.

  • And toward the end of this event, scientists spotted a bunch of nanojets streaking across

  • their images, perpendicular to the arcs formed by the coronal rain.

  • It was the first clear observation of this phenomenon, which was exciting.

  • But to be sure they were actually looking at what they thought they were, scientists

  • ran simulations to see if nanojets like the ones they observed would form under the existing

  • conditions on the Sun.

  • And the simulations checked out!

  • Together, these findings help back up a hypothesis scientists have had for years about the heating

  • of the corona.

  • The formation of one nanoflare can trigger another, and so on. So an avalanche of nanoflares

  • might generate enough energy to heat the atmosphere to the temperatures we measure.

  • Scientists will still need to keep an eye on the Sun to figure out how frequent these

  • nanoflares actually are and whether or not their energy is doing any significant heating.

  • But luckily, two solar spacecraft are on the way.

  • In the next few years, NASA's Parker Solar Probe and the ESA's Solar Orbiter will give

  • us an unprecedented view of the Sunand hopefully help us solve this mystery for once

  • and for all.

  • Thanks for watching this episode of SciShow Space News, which is produced by Complexly.

  • If you want to keep imagining the world complexly with us, check out Bizarre Beasts!

  • Each month, we'll introduce you to a new bizarre beast and explore what makes these

  • animals so weird to usfrom birds whose babies have claws on their wings to lizards

  • with glowing bones.

  • And if you want to take a bizarre beast home, check out the Bizarre Beasts pin club! You

  • can find a link for that and the channel in the description below.

  • {♫Outro♫}

{♫Intro♫}

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我们对火星上的地下湖了解得更多(We Know More About That Underground Lake on Mars | SciShow News)

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    joey joey 發佈於 2021 年 07 月 01 日
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