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  • The day has finally come.

  • Together we are going to leave Earth on a one-way trip to a new world.

  • The launch window is open.

  • Our rocket is fueled andall systems are go.”

  • So get ready as we go on a Mission to Mars.

  • You may be wondering why we are going to Mars instead of Venus.

  • After all, Venus is the closest planet to Earth, and it’s roughly the same size as Earth.

  • Sounds promising, right?

  • Well, there are a few problems with Venus.

  • Its surface temperature is over 450 degrees Celsius.

  • And the air pressure on the surface would quickly crush us.

  • Then there’s the little matter of clouds of sulfuric acid...

  • Mars by comparison is much more hospitable.

  • Sure well weigh a little less, and the air is unbreathable, but

  • we can survive these challenges.

  • Now, you’d better get comfortable because this trip will take awhile!

  • Were on our way!

  • We timed our trip to Mars for when it would be closest to the Earth.

  • Remember, planets travel in elliptical orbits, so theyre not always at the same distance

  • from the Sun, or each other.

  • Mars has one of the most eccentric (or least circular) orbits - only Mercury is more eccentric.

  • Mars makes a “close approachto the Earth approximately every 26 months.

  • But sometimes it gets even closer.

  • We say Mars is "at opposition" when it lines up with Earth on the same side of the Sun.

  • We get the name from the view on Earth, with Mars and the Sun onoppositesides of our sky.

  • When Mars is at its very closest point to the Earth, we call it a “favourable opposition.”

  • At this point, the distance between the two planets is only about 56 million kilometers.

  • We didn’t have too long to wait for a favourable opposition - this configuration happens about

  • every 15 years.

  • Keep in mind, we didn’t point our rocket right AT Mars when we took off.

  • Instead, we aimed for where Mars was going to be when we arrived.

  • The whole trip takes months.

  • If we went at the wrong time, the trip would take much longer, and we’d need a lot more fuel.

  • Were getting close to Mars!

  • Let’s take a look!

  • It looks red, doesn’t it?

  • That’s kind of an optical illusion.

  • The surface of Mars is a mix of colours including brown, tan, butterscotch...and the planet

  • is covered by reddish-brown dust from a variety of iron compounds.

  • That rusty-coloured dust gets kicked up into the Martian atmosphere, and when it’s lit

  • up by the sun and surrounded by the blackness of space, it looks red to our eyes.

  • Many early cultures named Mars based on its colour - the Egyptian priests were the first

  • to write about Mars around 2000 BC, calling itHorus The Red.”

  • Ancient Chinese astronomers called itThe Fire Star.”

  • The Greeks saw red and thought of blood, and named it after their God of War, Ares.

  • The Romans followed suit, and called it Mars, after their own God of War.

  • Let’s get a closer look at those reddish rocks.

  • If we turn on our spectroscope, we can see that the planet’s surface is

  • mostly made up of the minerals feldspar, olivine, and pyroxene.

  • Those minerals are found on Earth in solidified lava.

  • That means we should expect to see volcanoes.

  • We can start to make out the very thin atmosphere of Mars.

  • See that narrow ring?

  • The air is SO thin, were going to experience very low pressure.

  • And we won’t be able to breathe the air on Mars.

  • It’s about 96% carbon dioxide, and a little bit of other gases.

  • As we begin our descent through the atmosphere, we see a few wispy clouds.

  • These ice clouds are made of frozen carbon dioxide - ordry ice.”

  • As we continue to descend, we move through that dust layer.

  • Finally, we come across some water ice clouds.

  • You knew there was water on Mars, right?

  • This thin atmosphere isn’t going to provide much thermal insulation.

  • We can expect big temperature swings on the planet’s surface, from as high as 20 degrees

  • Celsius during the day, to negative 140 degrees Celsius at night.

  • Well definitely need a shelter.

  • Okay, everyone.

  • Brace for landing.

  • Home sweet home!

  • We had to quickly set up a habitat that provides us with air,

  • constant pressure, food, and water.

  • The air pressure outside on Mars is only around 1% of the atmospheric pressure we find

  • at sea level on Earth.

  • We’d have to travel well above the surface of the Earth, into the Stratosphere,

  • before we felt so little air pressure.

  • Youll notice I’m wearing a weighted suit, because Mars surface gravity is only

  • 37% of the Earth’s.

  • That means without the suit, I could jump a lot higher on Mars.

  • This suit makes walking around feel a little more normal.

  • Of course, when I go outside, I’ll need to change into a pressurized suit,

  • with a helmet.

  • I’m going to have to take some air to breathe along with me.

  • Now, time for a good square meal before we go out to explore.

  • Weve landed in the Northern Hemisphere, which is relatively smooth compared to the

  • heavily cratered South.

  • Will you look at that!

  • We have ourselves a mountain view!

  • That’s not just any mountain.

  • That’s Olympus Mons, the largest volcano in the Solar System.

  • It stands 25 kilometers high.

  • That’s about 3 times taller than Mount Everest.

  • Olympus Mons is what we call a “shield volcano.”

  • Rather than erupting violently, this kind of volcano gets built up

  • by lava flowing down the sides.

  • Shield volcanoes, like the ones in the Hawaiian islands, were named for their resemblance

  • to a soldier’s shield lying on its side.

  • Olympus Mons isn’t the only big volcano on Mars.

  • Around 1200 km away, there are three other giant volcanoes,

  • together called the Tharsis Montes.

  • Mars is also home to one of the largest canyons

  • in the solar system, Valles Marineris.

  • It’s about 4,000 km long, 200 km wide, and almost 7 km deep.

  • That’s unimaginably big.

  • Picture a canyon that stretches almost all the way from the East Coast to the West Coast

  • of the United States.

  • The depth of Valles Marineris allows us to make some estimates about the thickness of

  • Mars’s crust - it must be significantly thicker than the Earth’s crust to allow

  • for such a deep gorge, as thick as 35 km in the northern hemisphere, and even thicker

  • in the southern hemisphere (we call that a “crustal dichotomy”).

  • Before we go anywhere, were going to have to plan our sightseeing trip carefully.

  • After all, compasses don’t work on Mars.

  • That’s because unlike the Earth, Mars doesn’t have a magnetic field.

  • Were going to use Olympus Mons as a landmark, and head out from there.

  • Maybe we can take a boat ride down those famous Martian canals!

  • I’m just kidding.

  • Years ago, people used to think there were canals filled with water on Mars.

  • It turns out it was more a miscommunication than anything...

  • In 1877, the Italian astronomer Giovanni Schiaparelli described the straight lines he saw

  • crisscrossing Mars.

  • He called themcanali,” which meanschannelsin Italian.

  • English speakers misinterpreted the word ascanals,” which implied there were actual

  • Martians building an irrigation system.

  • The story quickly spun off into fantasy, with people imagining reasons for Martians transporting

  • water from the icy poles to the more equatorial regions: the Red Planet was a desert, running

  • out of resources, and that meant any day Martians were going to show up on Earth and take us over!

  • The idea of extraterrestrial life on Mars gave rise to timeless works of science fiction

  • from such greats as Edgar Rice Burroughs, HG Wells, and Ray Bradbury.

  • We now know there are no signs of engineering on Mars - no canals.

  • Even the grooves on the planet’s surface that Schiaparelli documented

  • turned out to be an optical illusion.

  • But there IS water.

  • Weve known about there being frozen water on Mars for a while.

  • There are polar ice caps, just like on Earth, made of frozen water.

  • But recently weve uncovered good evidence for RUNNING water on Mars.

  • Weve captured images of dark streaks in the same areas where weve identified

  • hydrated salts on the spectrometer.

  • These dark streaks change size with the seasons, suggesting seasonal flows of water.

  • We should be able to get a good look at these areas today.

  • Well have quite a few hours of daylight for exploring.

  • A day on Mars is about the same length as a day on Earth.

  • It takes 24 hours, 37 minutes, and about...23 seconds for the planet to rotate once.

  • Of all the planets, a Martian day is the closest to an Earth day.

  • The seasons are another story.

  • Like the Earth, Mars has an axial tilt.

  • That is, its axis of rotation is tilted about 25 degrees away from the perpendicular.

  • Earth’s axial tilt is 23.5 degrees.

  • This means both planets experience seasons, with opposite seasons

  • in the northern and southern hemispheres.

  • However, the Martian seasons are about twice as long as on Earth, because it takes Mars

  • almost 2 Earth-years to complete its orbit around the sun.

  • I can’t wait to get a look at that Martian sky - it’s brownish-yellow, because of the

  • red dust in the atmosphere.

  • The dust particles contain magnetite, which absorbs blue light, leaving the sky yellow.

  • Well also get to see the two moons orbiting Mars - Phobos and Deimos.

  • They were discovered in 1877 by American astronomer Asaph Hall.

  • He named the moons after the sons of Ares, the Greek God of War - Phobos means "fear,"

  • and Deimos means "rout."

  • You might mistake these two moons for asteroids - theyre small and irregularly shaped.

  • There’s some debate about how Mars got its two moons - did it capture a couple of asteroids?

  • Or are they leftovers from when Mars was first formed?

  • {{alarm goes off}}

  • {{ALARM IS RINGING}} Well, spaceballs.

  • Were going to have to scratch our little walk today.

  • There’s a dust storm brewing.

  • Mars gets massive dust storms, complete with whirlpools called Dust Devils.

  • Even though the wind exerts much less force here on Mars compared with the Earth, since

  • the air is so thin - were not going to take any chances.

  • Some of these storms can last for months, and stretch over the entire planet.

  • Killer dust storms, butterscotch sky, it’s a typical day on Mars.

  • As you can see, it’s not going to be so easy living here on Mars.

  • So what will it take to make Mars more hospitable to life?

  • On Earth, we have a nice thick atmosphere keeping the temperature fairly stable.

  • The greenhouse effect from gases like carbon dioxide keeps warming our planet,

  • making it suitable for life.

  • You might think, with such a high percentage of carbon dioxide in the air on Mars, we could

  • expect the greenhouse effect here as well.

  • But the atmosphere is just too thin.

  • And water vapor, which also helps stabilize Earth’s temperature, is present here

  • only in trace amounts.

  • Is there a way to transform this place - toterraformit?

  • Scientists are working out some proposals.

  • It comes down to 3 key elements: build up an atmosphere, keep it warm enough to sustain life,

  • and stop the atmosphere from leaking away into space.

  • One day...One beautiful Martian day

  • Thank you for watching!

  • Special thanks to Ray Bradbury for inspiring us.

The day has finally come.

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讓我們去火星吧||天文學||太空探險 (Let's go to MARS || Astronomy || Space Exploration)

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    林宜悉 發佈於 2021 年 01 月 14 日
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