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  • [♩INTRO]

  • In 2021, Mars is set to receive new robotic inhabitants.

  • But until then, we have other explorers hard at work

  • learning what makes the Red Planet tick.

  • Like NASA's InSight lander!

  • InSight touched down in November 2018,

  • and its first results were finally released this week in two Nature journals.

  • The results reveal a seismically active world with magnetic

  • and atmospheric phenomena, all begging for further investigation.

  • InSight lives in a sediment-filled crater in the Elysium Planitia region

  • a volcanic plain a bit north of where Curiosity is.

  • Its mission is to learn what it's like beneath Mars's surface.

  • And to do that, it brought along some really cool instruments.

  • For one, it has Mars's first seismometer in forty years!

  • At first, that could seem like a weird thing to bring to Mars.

  • Because until recently, we thought the planet was geologically dead,

  • with not an earthquake, or... a marsquake, to be found.

  • But the hope was that this seismometer could at least help us learn about

  • other seismic activity, from things like meteorite impacts or dust devils.

  • And it delivered!

  • As of September, InSight had recorded 174 seismic events.

  • And at least twenty-four of them bore resemblance to minor earthquakes.

  • Now, Mars doesn't have tectonic plates,

  • the main thing that causes earthquakes here at home,

  • but this suggests it still has some kind of quakes!

  • So, Mars isn't dead after all!

  • We're still learning how these things work, but they may be caused

  • by Mars's continual cooling over the billions of years since it formed.

  • As it cools, it contracts, which applies stress.

  • And given enough time, the material under stress could break, causing a quake.

  • These twenty-four events happened so deep

  • that you and I probably couldn't feel them from the surface.

  • But InSight could!

  • And by looking at how the vibrations travel through the planet,

  • it could teach us about Mars's geology and what the planet is made of.

  • Besides the seismometer, InSight also has

  • the first magnetometer to grace the Martian surface.

  • Mars doesn't have a planet-wide magnetic field anymore,

  • but some of the rocks deep in its crust are still magnetic.

  • And InSight's instrument can detect that.

  • So far, it's measured the strength of these local magnetic fields

  • and how they change over the course of the day.

  • But it's also teaching about Mars a whole.

  • Given how deep these rocks appear to be buried,

  • scientists estimate they're about 3.9 billion years old.

  • That's slightly younger than when most scientists believe

  • Mars's planet-wide magnetic field shut down,

  • so it could mean that field lasted a little longer than we thought!

  • Finally, this is all cool, but InSight is leaving us with a few mysteries, too.

  • Like, its atmospheric instruments found that night-time gravity waves

  • are more abundant than prior data suggest.

  • Gravity waves are regular, periodic changes in air pressure, temperature,

  • or wind speed, caused by changes in the air buoyancy.

  • And they're entirely different from gravitational waves,

  • the distortions in space-time we detect when black holes collide.

  • But despite seeing them on Mars, we don't really know what they mean.

  • InSight also found the first evidence of infrasound on Mars

  • sound waves with frequencies lower than what we can hear.

  • But again, we're not sure what that can teach us.

  • So there's a lot left to learn!

  • And we're also waiting for two of InSight's other instruments,

  • including its heat probe, to collect enough data to publish.

  • Fortunately, the mission was expected from the outset

  • to take twenty-four months to meet all its objectives,

  • so our little lander is still on track.

  • In related news, Mars's two lumpy moons,

  • Phobos and Deimos, are scheduled to get their own visitor!

  • Last week, the Japanese Space Agency JAXA announced

  • that their Martian Moons eXploration mission, or MMX,

  • has entered the development phase.

  • That means it's no longer just a research project:

  • Engineers can officially start developing hardware and software.

  • Mars may have two moons to Earth's one, but they're way smaller.

  • On average, Phobos is only twenty-three kilometers across,

  • roughly the length of a half-marathon, and Deimos is about half of that.

  • We're also not sure how Mars got them.

  • They may have started in the asteroid belt,

  • then been flung towards Mars by Jupiter's gravity.

  • Or they could have formed like Earth's moon probably did:

  • from the debris left over after something smashed into Mars.

  • One way to answer this question would be to study the moons's compositions

  • and see how similar they are to Mars itself.

  • And that's what MMX will do!

  • After surveying both moons, the spacecraft will land on Phobos

  • and collect at least a ten-gram sample

  • from at least two centimeters below the surface.

  • Then, it will return that sample to Earth for analysis.

  • No one has ever gone to Phobos like this,

  • but sample return missions are no stranger to JAXA.

  • Their Hayabusa2 probe is currently on its way home

  • carrying a bit of the asteroid Ryugu.

  • But the MMX mission takes further strides by collecting more material and by

  • using a corer instead of a tiny cannonball to blast material off the surface.

  • The craft will also have to navigate another planet's gravitational field,

  • rather than visit a space potato freely orbiting the Sun like Ryugu.

  • But it will be worth it!

  • Besides helping us understand where the moons came from,

  • studying bits of Phobos will help scientists answer questions

  • about the history of water in the solar system.

  • For instance, if the moon formed from Mars,

  • it could carry a record of Mars's watery past.

  • Or if it formed in the asteroid belt, it could help us understand the space rocks

  • that may have brought Mars and Earth their water early-on.

  • The mission will also provide a look at how Mars has evolved in general

  • over billions of years.

  • That's because both moons are suspected of accumulating material

  • kicked off the planet's surface during meteorite impacts

  • bits thrown into the air fast enough to wind up in space!

  • MMX will even help determine how humans could visit these moons

  • and collect samples themselves.

  • Under the current timeline, MMX is looking to launch in 2024

  • and return before the end of the decade.

  • Which, conveniently, leaves us plenty of time before Phobos

  • is scheduled to be ripped apart by Mars's gravityin 30 to 50 million years.

  • So, we've got some wiggle roomand plenty to learn in the meantime.

  • Thanks for watching this episode of SciShow Space News

  • is brought to you by today's President of Space, Matthew Brant!

  • Matthew is one of our patrons on Patreon, and they,

  • along with the rest of our Patreon community, help make this show happen.

  • So, thanks, Matthew!

  • We wouldn't be able to talk about this much cool space stuff without you.

  • If you want to become our next President of Space or just help support the show

  • in some other way, you can learn more at Patreon.com/SciShow.

  • [♩OUTRO]

[♩INTRO]

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    林宜悉 發佈於 2021 年 01 月 14 日
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