Name: 也許火星上沒有液態水 (Maybe There Isn't Liquid Water on Mars)
Uploaded: 2021-01-14T10:41:31.000Z
Duration: 6 min 27 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

轉承詞

Two years ago, the entire scientific community—including us—freaked out because researchers discovered

flowing liquid water on the surface of Mars.

程度副詞

According to a paper published on Monday in Nature Geoscience, it might just be… sand.

Y'know, sand is coarse... and rough.. and gets everywhere.

Since life on Earth relies on liquid water, we're always searching for it in other parts

of the solar system, in case it contains alien bacteria or can teach us more about our planet.

And thanks to previous missions, we've found that Mars has plenty of water frozen in polar

ice caps or floating around as water vapor.

But in 2015, researchers announced that they'd found liquid water trickling down hills on

Specifically, they found hydrated salts, which are just salt molecules attached to some water molecules.

And these hydrated salts created dark, flowing lines on Mars' surface called recurring

On the off-chance life was hanging out in those RSLs, we didn't want to send the Curiosity

rover to check them out, because it's contaminated with material from Earth.

But scientists have been analyzing them with satellites.

In this new paper, they used the HiRISE satellite orbiting Mars to study the slopes of more

They found that, on average, almost all of the RSLs ended when a hill got between 28

And, according to measurements of Martian sand dunes, that's about the same angle

The scientists argue that, if the RSLs do contain liquid water, some of them should

Still, that's not the only reason they're questioning the liquid water idea.

For one, if RSLs were filled with salty water, they should be depositing dry salt piles when

the water eventually evaporates, but scientists haven't found any yet.

Also, one of the arguments for RSLs containing water is that they appear seasonally, like

But this team observed that sand flows can also change seasonally, based on how dust

Still, this definitely isn't a perfect hypothesis: The researchers admitted that seasonal sand

flow happens more easily on certain dunes that are constantly replenished by new sand

And the hills where we've seen RSLs aren't all like that.

And sand can't explain the hydrated salts, either.

Previous studies, like one published last year in Geophysical Research Letters, have

suggested that they could be caused by carbon dioxide frost instead, which would form when

gas condenses and freezes on the surface.

So before you throw your swimsuit into your bag and put it on your Mars rocket, maybe

wait a little while until we know a little more.

But don't abandon your suitcase entirely!

Because last week, astronomers announced that they've found a new, nearby exoplanet that

It's called Ross 128 b, and it was spotted using HARPS, an instrument attached to a telescope

HARPS is one of our most successful tools for finding new worlds.

It discovers planets by measuring wobbles in stars, which suggest that something — like

This new planet orbits a red dwarf star only 11 light-years away, making it the second

closest Earth-like exoplanet we've found.

Proxima Centauri b is just about 4 light-years away.

Red dwarfs are the most common stars in the universe, and they can be great exoplanet

They're only half the size of the Sun at most, and aren't too bright or hot.

And, while some of them can give off the occasional violent burst of radiation, the star 128 b

From what we know so far, Ross 128 b doesn't seem too different from Earth.

It's about the same size, and its temperature probably ranges from -60 to 20 degrees Celsius.

But since its star is so small, 128 b orbits it a lot more closely than we do the Sun — about

This helps it stay nice and warm, but it also means a year there lasts a little less than

But if you don't mind birthday cake, that's not so bad.

Right now, even though the planet seems homey, we're not sure what its atmosphere is like,

or if it has liquid water on its surface.

But when the European Southern Observatory's Extremely Large Telescope comes online in

2024, it should be able to figure out if 128 b has any oxygen in its atmosphere.

For now, it's still the most temperate planet we've ever found around such a calm star,

And we'll be learning more about it soon.

Plus, 128 b's star is currently cruising toward our solar system, and in around 70,000

years, it'll be the closest star to Earth besides the Sun.

So if we're still around in 70,000 years, but still haven't got warp drive figured

out, at least the trip will be a little shorter if we do decide to go.

The SciShow team and I were talking about a problem that many of us have.

Often, people will ask us what we want for Christmas, or for our birthdays and we won't

know what to say because we don't care about stuff that much.

But then I was thinking: there are things that I would like to get, or that I've bought

for myself, or that people have given to me that I really love because I love the world,

I love the universe, the existence of biology...that kind of thing.

So we put together a collection of artifacts of this universe...we got a limited number

of each of those things, and we have put them up at a store called SciShow Finds.

The SciShow Finds are curated by me, they are things that I would love to get in my

It's a very small list of just six cool things of varying price points.

I did my best to only include one science book.

It's the book that I read this year that affected me the most, it's called "What is

Life" and it makes an extremely compelling case that biology is a chemical inevitability.

Which is a really important thought for having there be life out there in the universe.

As time progresses, we're probably going to add some new finds.

And as we add new ones, they will replace the ones, so all of these products are only