Placeholder Image

字幕表 動画を再生する

  • {♫Intro♫}

  • Earth has had a complicated relationship

  • with asteroids. Just ask the dinosaurs.

  • Oh, wait

  • Still, it's not always fire and brimstone, and according to a new study, asteroids might

  • actually benefit life on our planet sometimes.

  • The paper was published last week in the journal Science Advances. And in it, researchers suggest

  • that a huge asteroid may have driven one of the largest increases in biodiversity in Earth's

  • history.

  • Almost five hundred million years ago, during what scientists call the Ordovician period,

  • Earth looked pretty different.

  • Back then, most life existed in the ocean, and most land was clumped together in a giant

  • supercontinent.

  • The climate was also warm, and the planet had nearly no ice, even at the poles.

  • Then, around four hundred sixty-six million years ago, Earth began to enter an ice age.

  • Scientists have long wondered why this happened, and this new research suggests the cause may

  • have been in space.

  • See, around this time, an asteroid about one hundred fifty kilometers across broke apart

  • between the orbits of Mars and Jupiter.

  • It's not clear why it happened, but it was a big dealperhaps the largest breakup

  • since the solar system settled down more than three billion years ago.

  • In fact, even today, around a third of all meteorites falling on Earth seem to come from

  • that one body.

  • Researchers have suspected there might be a connection between this asteroid's destruction

  • and the Ordovician ice age, but no one was able to provide detailed evidence until now.

  • In this work, researchers measured the ages of ancient sediment layers and fossil meteorites:

  • objects that hit Earth in the distant past and became part of that era's geologic record.

  • That allowed them to demonstrate that the timing of the asteroid breakup almost perfectly

  • matched the start of that ice age.

  • As for why this space rock had such an effect? Well, their evidence also showed that the

  • breakup dumped a lot of dust into the inner solar system.

  • Every year, Earth gets hit by about forty thousand tons of interplanetary dust. But

  • after the asteroid breakup of the Ordivician, that amount increased by a thousand or even

  • ten thousand times.

  • The paper suggests that this dust blanketed the Earth's upper atmosphere for about two

  • million years, blocking some of the Sun's heat from reaching its surface.

  • And that likely resulted in a global cooling that transformed Earth's ecosystems.

  • Before, habitats were all kind of just… “warm.” But after, the poles were cold,

  • the equator warm, and the tropics somewhere in-between.

  • We'll need more research to say exactly how and why this happened.

  • But one way or another, as life evolved to adapt to this new environment, it diversified

  • dramatically.

  • Seriously, the variety among groups of species quadrupled to something more like modern levels.

  • Not all species could adapt to these changes, though, and the end of the Ordovician is also

  • marked by the first recorded global extinction, in which eighty-five percent of species perished.

  • So it wasn't a good time for everyone. But one way or another, this study is a cool reminder

  • that life on Earth isn't just influenced by what happens on our planet. It's part

  • of a much larger systemone that sometimes involves asteroids millions of kilometers

  • from here.

  • Now, while some researchers are studying the past, others are looking to the future. A

  • future where humans are living on Mars.

  • With recent advances in commercial spaceflight, sending humans safely to the Red Planet may

  • soon be possible. So it's not ridiculous to think that decades from now, we might want

  • to start a big settlement there.

  • If we do, one of our biggest challenges will be providing our own food, since shipping

  • meals from Earth won't be practical for long. And it's a challenge scientists are

  • already researching.

  • In a new paper, a pair of researchers at the University of Central Florida investigated

  • what it would take to develop a food-independent Mars society with one million people.

  • And they found it will take compromise — a whole lot of compromise.

  • For one, they propose that there almost certainly won't be much farm-raised meat.

  • After all, raising livestock requires a ton of resources and lots of space, which isn't

  • very scalable on a planet without breathable air.

  • One substitute might be to develop lab-grown meat, which has many of the caloric benefits

  • without all themoo.” But that's really still in an experimental phase.

  • So instead, the team suggests animal protein could come from insects, which are nutrient-rich

  • and can be farmed in a small area.

  • This need to conserve space and find calorie-dense crops is a consistent theme in the paper.

  • For example, it also proposes that corn, soybeans, and peanuts would make good staple crops.

  • But then again, even once you figure out what to grow, you still need to figure out how

  • to grow it. And there are some challenges there, too.

  • Like, the best long-term solution for farming on Mars is to grow crops in actual soil. But

  • the authors note that would take time to convert the dead, poison-laden Martian regolith into

  • something that can safely grow plants.

  • In the meantime, we'd likely need to use hydroponics, a method of growing plants in

  • nutrient solutions instead of soil. Except, while that's more compact and would let

  • you get started right away, it would require us to ferry more heavy equipment from Earth.

  • Realistically, these aren't problems we'll need to worry about soon. But overall, this

  • paper makes a good point: An early Mars settlement will be really dependent on Earth.

  • Whether it needs equipment or heaps of pre-packaged meals, it will require millions of tons of

  • supplies to be shipped across the solar system.

  • With today's tech, that would come at a staggering cost. But maybe by the time we're

  • ready to support a million people on Mars, we'll have figured this out.

  • Thanks for watching this episode of SciShow Space News, and special thanks to our patrons

  • on Patreon! If you're a patron, let us know what you think about this episode in our new

  • Discord server. And if not, we'd still love to hear your thoughts in the comments.

  • If you do want to learn more about becoming a patron, you can head over to patreon.com/scishow.

  • {♫Outro♫}

{♫Intro♫}

字幕と単語

動画の操作 ここで「動画」の調整と「字幕」の表示を設定することができます

B1 中級

古代小惑星が氷河期を引き起こした?| 小惑星が氷河期を引き起こしたのか? (Did This Ancient Asteroid Cause an Ice Age? | SciShow News)

  • 2 0
    林宜悉 に公開 2021 年 01 月 14 日
動画の中の単語