Mars: Crash Course Astronomy #15

Mars: Crash Course Astronomy #15

Hey folks, I’m Phil Plait and this is Crash
Course Astronomy. You know, I can’t think of any object in the sky that’s captured
our imagination like Mars has. The Red Planet was once thought to be the god of war, and
in more modern times has been the setting for a zillion science fiction novels, movies,
TV shows, and more. And now that we’ve gone there, landed there, roved there, it’s become
far more than a simple background for an alien invasion story: It’s become a world, a place…
and maybe, one day, a destination. Mars is the fourth planet from the Sun, and
the outermost of the terrestrial planets; that is, ones that are rocky and similar in
size to Earth. It orbits on average a little over 200 million kilometers from the Sun.
That puts it outside Earth’s orbit, and it never gets much closer to us than about
60 million kilometers. It’s colder than us, too, with an average surface temperature
of about 60 below 0 Celsius. It’s not a terribly big planet; it’s only about half
the size of Earth. Still, when it’s closest to us in space it shines brightly in our night
sky, a red beacon glowering like an angry eye. No doubt this is why ancient civilizations
associated it with war! But it turns out Mars isn’t red because it’s bloody. It’s
red because it’s rusty. Literally. That red color you see comes from fine-grained
dust on the surface, almost like ruddy talcum powder. The dust is rich in iron that’s
oxidized, forming rust. The dust coats a lot of the surface, giving it a butterscotch or ochre
coloring, and also gets blown into the atmosphere. A lot of the surface of Mars is also grey
volcanic rock called basalt, and together with other minerals gives Mars its overall
reddish look. We can get a decent view of Mars from Earth
using telescopes, but small features are maddeningly difficult to tease out. The idea of a clement environment on Mars
stuck with us, though… at least until the 1960s and 70s, when we started send probes
to the planet. They did not see a lovely, habitable world: Instead, what we got were
photos of a dry, dead, forbidding planet. The surface geography of Mars is weird. There’s
a huge dichotomy between the northern hemisphere, which is mostly smooth plains, and the southern,
which is cratered, hilly highlands. Apparently, Mars suffered a tremendous impact from an
object hundreds of kilometers across eons ago. It left behind a vast basin near the
north pole of the planet, which filled with lava. Topographic maps show the northern hemisphere
has much lower elevations than the southern, and can be depressed by several kilometers.
Walking from the south to the north pole is essentially all downhill! Another large feature is the Tharsis bulge,
a huge plateau that’s home to the four biggest volcanoes on Mars, and the largest volcanoe
in the solar system: Olympus Mons. Mars doesn’t have plate tectonics today, but there’s
evidence it once did. Tharsis was probably over a hot spot, a plume of hotter material
rising up through the planet’s mantle. That’s what may have created the bulge, and as the
plate slowly moved the plume punched through the crust to create the chain of three smaller
(but still huge) volcanoes. But the grandest of the surface features on
Mars is easily Valles Marineris; a canyon discovered when the Mariner 9 probe orbited
Mars in the 1970s. It’s a gigantic crack in the surface of Mars 4000 kilometers long,
200 kilometers wide, and 7 kilometers deep. That’s 10 times longer and 10 times wider
than the Grand Canyon! Unlike the Grand Canyon, it wasn’t carved by water; it may have formed
when the Tharsis bulge rose up, creating the valley as a radial crack in the surface. Mars, like Earth, has polar ice caps. Both
are mostly water ice, several kilometers thick, but they get seasonal coatings of dry ice,
frozen carbon dioxide, that covers them from 1 to 8 meters thick. This happens in their
respective winters; in the summer, sunlight thaws the CO2, turning it directly into a gas which then
blows away from the pole, generating fierce winds. Speaking of which, Mars has an atmosphere,
but it’s thin. Pressure at the surface is less than 1% of Earth’s, and the air is
mostly carbon dioxide. In fact, as much as a third of the Martian atmosphere freezes
out every winter to coat the polar ice caps! The air doesn’t provide much of a shield
from asteroid and comet impacts, so the surface is heavily cratered—and it still gets hit
today. The space probe Mars Reconnaissance Orbiter has been circling Mars so long, it’s actually
seen new craters from fresh impacts on the surface! However, the atmosphere is substantial enough
to interact with the surface. Winds blow seasonally, filling craters with the ubiquitous dust.
There’s also sand on Mars, made of eroded basaltic rock, so it’s grey. The wind blows
this into beautiful dunes, including series of parallel ridges in crater floors, and barchan
or horseshoe-shaped dunes. Mars also gets dust devils, towering vortices
of wind similar to tornadoes. These dust devils have been seen from orbit, and when they blow
the red dust around on the greyish basaltic plains, they can leave behind incredibly complex
and beautiful curlicues. One of my favorite recent discoveries about
Mars is that it has avalanches! There are lots of cliffs towering above the surface,
and in the spring, when buried frozen carbon dioxide thaws, it can dislodge material, creating
tremendous cascades of rock and dust. Several of these have been caught in the act by orbiting
space probes. Mars has two moons: Small, potato-shaped rocks
named Deimos and Phobos. Both are tiny; Phobos is about 25 kilometers across, and Deimos
just 15. Both look very much like asteroids, and may indeed have been captured by Mars
from the nearby asteroid belt. To be honest, though, it’s not clear what their origins
are. Phobos orbits Mars only 6000 km over the surface,
and it moves so rapidly in its orbit that it orbits faster than Mars rotates; from the
surface it appears to rise in the west and set in the east. Tides from Mars are altering
its orbit, slowly lowering Phobos closer and closer to the surface. In a few million years,
it’s expected to drop low enough to actually enter the atmosphere and impact the surface.
That’ll be really exciting to watch …from a safe distance. Incidentally, from some locations on the surface,
the moons can be seen to transit the Sun, passing directly across its face. The rovers
on Mars have taken lots of pictures of these events, which is pretty cool. So Mars has rocks, air, weather, and volcanoes…
but what about water? If it has frozen water at the poles, what about the rest of the planet? We know there’s water ice at the mid-latitudes
of Mars; some recent small asteroid impacts have white area around them; underground deposits
of ice splashed out by the impact. There’s no strong evidence of liquid water on the
surface of Mars right now though. Some crater walls collapse a bit and have dark channels
running down them, which look like they could’ve been carved by flowing water, but there are other
possible sources too, so their cause still isn’t certain. But in the past, things were different. Mars
was once very wet. There’s tons of evidence for flowing water on the surface long ago,
including dry river beds, dry lakes, sedimentary layers, and minerals we know need water to
form. There’s even evidence Mars had oceans. But that’s all gone now. What happened?
It’s not clear. Billions of years ago Mars was almost certainly warmer and had a thicker
atmosphere. But for some reason, its internal dynamo shut down, and its magnetic field disappeared.
This left it vulnerable to the solar wind, and over billions of years the Martian atmosphere
was eroded away. The water went with it. This raises another obvious question: If it
had air and water, could it have had life? That question wasn’t taken terribly seriously
just a few decades ago, but now we’re very interested in it, enough to spend a lot of
money sending probes to Mars to look at what conditions for life are like now and once
were in the past. It’s still an open question, and we know life on Earth got its start not
long after the surface cooled. Mars is smaller and cooled more quickly after its formation,
so it’s not crazy at all to wonder if life formed there, even before it did here. Intriguingly, the Curiosity rover detected
simple organic molecules in a rock sample—this doesn’t mean there’s life, but it means
the ingredients were and are there. It also detected a brief spike in methane, a volatile
gas that can be produced by life… as well as by other, geologic processes. The evidence
we have right now is maddeningly vague, but we’re just starting out. Give it time! Mars isn’t the same planet it used to be.
But that doesn’t mean it’s off limits. Getting to Mars is hard—over half the missions
sent there have failed—but not impossible. We’ve had amazing successes, including orbiters,
landers, and rovers. I’d say we’ve learned as much about the Red Planet in the past couple of decades
as we had in all the centuries of study before them. Still, all we’ve sent are robots. They’re
good, and relatively inexpensive, but they’re slow. They can only cover so much ground.
A human could do as much in a week as a rover could in years… but humans are fragile.
We need water, air, food; we aren’t terribly tolerant of radiation or vacuum. But the idea of sending people to Mars isn’t
as nuts as it might have once been. We’re getting better at building rockets, and the
tech needed for human exploration of Mars is being developed now. There are even discussions
about landing sites, and where to build bases. One interesting idea is to use lava tubes—underground
caverns created by ancient lava flows, where the top of the flow cooled and created a roof.
We know these exist on Mars because we’ve seen holes in the roofs, called skylights,
openings to the cavern below. This would provide shelter from solar radiation, protection from
weather—Mars can get some pretty nasty dust storms in the spring—and could be sealed
up and filled with air. From there, a lot of the planet could be explored, and in a few years we’d once
again dwarf everything we’ve learned up to that point. I can’t say when this’ll happen—20 years
from now, maybe 30 or more—but it’ll happen. Eventually, there will be life on Mars. And
it’ll be us. Today you learned that Mars is smaller and
colder than Earth. It has polar ice caps, and lots of rusty dust covering its surface.
It also has the solar system’s largest volcano and valley. It’s dry now, but once upon
a time was much warmer and wetter, with a thicker atmosphere. It may even have had life. Crash Course Astronomy is produced in association
with PBS Digital Studios. Head to their channel to discover more awesome videos. This episode
was written by me, Phil Plait. The script was edited by Blake de Pastino, and our consultant
is Dr. Michelle Thaller. It was co-directed by Nicholas Jenkins and Michael Aranda, edited by Nicole
Sweeney, and the graphics team is Thought Café.


  • Steven Wilson says:

    Rust on the Earth's surface is indicative of the production of Oxygen which is because of life. How did Mars get all this oxygen to create rust if no life?

  • Ryan says:


  • Masta Blasta says:

    Those silly earthlings think they can they can claim mars.

  • Jaime Garcia says:

    The Moon SCRAPED IT

  • BWM SRRN says:

    Poor Mars is going to get invaded by humans one day. Lol just kidding, Mars doesn't have feelings.

  • Lisa Nikolich says:


  • karolak kolo says:

    I like how there is Falcon Heavy on the right side of the screen at 8:52. Where's my SpaceX fans?

  • K0BYN says:

    Do you think maybe we, or some form of human, use to live on Mars. Maybe we destroyed it so bad that it made our own race extinct. What if we sent life to earth as a last ditch effort to save our spieces. And now what if we are doing the exact same thing to earth? Maybe millions of years from now someone will make a video from Venus talking about earth and how it could've once sustained life. Freaky

  • ishaan satish says:

    Hello to all the future BFR Passengers Watching this for research

  • Jack Land says:

    did you know every year the mars rover sings "Happy Birthday" to itself
    give it time Bowie
    we may answer your question
    is there life on Mars?

  • Nirvana Amjad says:

    Can someone send me a list of the books Phil has on his desk? I can't make them out, and I'd love to read them a l l. Reply if you recognize any!

  • Logan Anderson says:

    I hope that within my lifetime mars will become the haven for life that it used to be. Such is a dream that I hold to.

  • you238 says:

    Mars may not be bloody, but it's still pretty profound that our blood and Mars are red for the same reason; iron compounds. We are made of Mars stuff.

  • Mohamed Medhat says:

    Watchin it in 2018

  • Giggly Kat says:

    They have already decided the landing sights.

  • Giggly Kat says:

    I want to go to Mars!! It's interesting!

  • Zane Robson says:

    Why it’s red is because iron oxide ok

  • Aug Steyr says:

    What about the crystal tubes found in the surface?

  • Fìrê Phõènîx says:

    then we fight there,destroy lands, lands andthen we destroy the whole new planet

  • Terezi Pyrope says:

    anybody else see the enterprise?

  • Charliezard The Arsonist says:

    A better comparison for Valles Marineris might be the Red Sea: 3 km deep, 350 km wide, and 2200 km long. (Valles Marineris is 4000 km long, 200 wide, and 7 deep, in case anyone was wondering but didn't want to scan back through the video.)

  • Will Huey says:

    one of the biggest mysteries about mars is what exactly happened to life on the planet.

  • egor Nye says:

    Answer key

  • Rayan Faure says:

    Tourist rail river still rest night various treatment virtue slide.

  • Ryan says:

    If we set up colonies on Mars could it be possible that those colonies could become independent nations like when Europe colonized the Americas?

  • Darkchylde50 says:

    Them keelow-meeters hurt the feelings of them kiluhmeh-ters..

  • shrestha bageshwar says:

    is mars in the goldilocks zone?

  • sre family says:

    unlike any teachers in school… he can teach us science.

  • Mashu says:

    in the beginning of the intro it says "One giant leap for mankind," but once you hear, "Brought by a freak for mankind," you hear the latter anymore.

  • Mashu says:

    Never drink the water from mars

  • Fe Simco says:

    I know so much about Mars thanks to Kim Stanley-Robinson's Red Mars series. If you're interested you should absolutely read it

  • Ygor Cortes says:

    Oh, I definitely did not know Mars was SO cool!

  • androkguz says:

    And then, Mars will declare it's independence from the UN and a two-century-long interplanetary cold war will begin

  • علاوي الموسوي says:

    انا احبكم

  • Ankit 4747 says:

    Forget about mars , Save earth

  • Oumaumau says:

    Sorry if this is a stupid question, but can the Oxygen in the Iron Oxide Dust, be used to create oxygen for Colonists?

  • Rebaz Ali says:

    Thank you for explaining everything in the metric system 🙂

  • XMrSurrealisticX says:

    01001000 01101111 01101101 01100101 00100000 01010011 01110111 01100101 01100101 01110100 00100000 01001000 01101111 01101101 01100101 00100000 00111010 00101001

  • Feynstein 100 says:

    If we could terraform Mars, it really would be a red, dead redemption 😀

  • Abhinav Verma says:

    No comments here after that the lake is discovered?

  • Beyblade Guy says:

    I had to watch this because we use him for out school I won’t hear yesterday so I had to watch this

  • Rahil Sethi says:

    Rusty or Bloody, one in the same thing. Our blood is red because it is rusty.

  • coweatsman says:

    I don't see any business model for sending people to Mars which would be more competitive than robots and AI. It's increasingly hard to build a case for humans in an earth based economy and earth is far friendlier than Mars for people. AI is only going to improve and people will always be fragile bags of mostly water. A Martian economy would operate best without people.

  • Matthew Moser says:

    I mean, we could go now, it's just a question of if we are willing to spend so much money on doing it.

  • Daniel Burke says:

    If we ever colonize another planet in the solar system it should eventually be venus. we just need to figure out how to get it spinning again to reactivate the electromagnetic field and help relieve some of the greenhouse effect. This could be done with a series of close passes with large asteroids over time and eventually putting one in a stable orbit as a moon. then impact the surface with comets to reintroduce water. obviously this would take many hundreds of years if not thousands and a serious increase in technology.

  • Gene Reyva says:

    Hopefully terraforming efforts for Mars won't consist of Cockroaches and Algae.

  • Freddy Pedraza says:

    "There's sand there too"
    Vader: target that red planet!!

  • Jackson Cahall says:

    Remember the Cant!

  • Aaron E says:

    It had life back when our distant ansestors lived there.

  • JRJN says:

    Why does the size of planets change so drastically between Mars and Jupiter?

  • Ming Fung says:

    So Mars is a red state and the earth is a blue state.

  • Kandela Brown says:

    Just send better robots.

  • Aaron Long Huynh says:

    If humans landed on Mars, would they be the Alien Invaders?

  • KHundead Gaming says:

    5:14 POTATOES

  • Ayesha says:

    not to be rude but wont we already be in an ecological crisis in 40 years?? feels like we're running out of time to make these discoveries

  • Juan Pablo Barbosa says:

    And, it's the only known planet populated only by Robots!

  • UpcominLegend says:

    Maybe Mars was hit by a GRB

  • Jerushah Stines says:

    Why does he say kilometer like "kill-o-meter"? I didn't think that was the correct way to pronounce it. I thought the correct way too say it is "key- lom-it-or".

  • Crystal Dreams says:

    Operation Highjump. and Newswabia google it

  • Crystal Dreams says:

    Also know nasa will not tell us that other humans and humanoids live on other planets, and have for thousands of years. and ancient peoples had advanced spacecraft etf.

  • Graphiar says:

    This is the only YouTube channel I keep watching even after graduating high school

  • Heliarc Master says:

    We came from Mars.

  • Frisk the human says:

    I just saw Jupiter, mercury, and mars next to each other in the sky!!!

  • Cara Miles says:

    5:11 I always thought it was pronounced "Dee-mos"?

  • Funtime Freddy says:

    Nothing last forever, we can change the future

  • Chaos A.D. says:

    🎅 lives at the North Pole. He just didn't say which planet.

  • Fab Antonio says:

    R.I.P. Curiosity Rover

  • Mariza Beci says:

    I learnt a lot.

  • gamingwithjackson says:

    what will happen when the sun get bigger?

  • donutworrybehappy says:

    The answer to all of life's mysteries: It had a collision with something else

  • paul skillman says:

    Look at Venus Look at Mars. Earth should be very worried. We take so much for granted on our planet. Our oceans must have saved us.

  • Madison Gass says:

    Watching this is 2019 is like: Yes, actually there is flowing water on the surface of mars.

  • OctavKitty says:

    If only we could make the dynamo inside Mars function again. So it could have a magnetic field. That would be a great start for life there

  • snurk agurk says:

    Tried to talk to mars, he gave me the cold shoulder

  • Tanwisha says:

    I have seen other astronomy videos on yt but no one beats Phil Plate when it comes to explaining complicated and fascinating facts with such ease and enthusiasm.

  • Iso specs says:

    Isnt is kinda funny we wanna go to a planet that is doomed to have a huge impact?

  • marco garza says:

    You guys wanna know who saved the universe he's name is Mark William Garza 😇🤕😢🤖👽👾👻💀👽 he's is the chosen ones

  • Nicholas Mitchell says:

    15 episodes in and I just peeped the Kerbals in the backdrop 😁

  • M Bayrak says:

    A renowned Turkish geology professor, Celal Şengör once made an experiment of that canyon in 3:24 , and is seriously claiming that it may be formed by collapsed icebergs and solid ice that had been heated by the magma. His theory was that there were huuuge water sources under that canyon, then the rising magma evaporated the solid ice, and the canyon just collapsed.

    He even made an experiment on it, and aired it on television in Turkey, and was in touch with Nature magazine to have it tested as a serious hypothesis.

  • venkata padmavathi says:

    your classes are very good sir

  • Connor Orr says:

    6:35 hm!

  • freddan6fly says:

    Love that you are so enthusiastic about the subject of space, a great video in a great series.

  • Kile B says:

    Wake up everybody nobody's going to live on Mars PERIOD! Watching a Ted talk about growing a potato there yet they have no clue about it's atmosphere magnetic pull and so on . .

  • Dorothy Isidro says:

    🔴 Mars

    ⚫ Deimos

  • Mike Or says:

    NASA plans to have humans land on Mars by 2035, but Elon Musk thinks that it will be done by 2025, or possibly even before that.

  • Asura Mabon says:

    That ice on Mars should be harvested and sold bottled for a fortune …
    ' Drink water from a time where there was no God ' 😉

  • Padraig McMahon says:

    Jupiter Doitis lier Doitis pansy on Fire🔥 Stoll HopBphone🌔🔴Jess Course🌔○ 🌒MA🔴RS🌔owen Red Owens Doitis Jupiter Doitis Hack and Friends Facebook Doitis Hackers Friends Doitis liers Friends Ring÷Supernova🌟○🌒🔴 deep in Spaces boertx Domind Thomas McMahon🌘🌠Thomas♈🔺️🔥♠️McMahon♈(🔥×🔥) Unknown Slbart Dimion bright🌟Green🌟Star AIRES Naver work for Jupiter Doitis lier pants on Fire🔥

  • Padraig McMahon says:

    Jupiter Doitis trick HOBSPHON Jess Course for my Sart Supernova Deep in spaces boertx Domind Thomas McMahon goin Unknown Slbart AIRES

  • Padraig McMahon says:

    KARM!♈420🔺️🔥♠️🌘MA🔴RS Domind🌒Supernova🌟 Deep in spaces boertx Goin ¿☆? HOBSPHON ¿🌔? With Jupite Doitis lier pants on Fire🔥 Unviers Friends halp lier Doitis Hacker Doitis Course don't Devers be call Course÷Doitis÷(🔥♈🔥)Thomas McMahon 🌒♈🔴÷🔵♑MA🔵RS ware Moom Doitis how yea No Moom Destroyed them come Sart Fack👑KING Jupiter Doitis Joick on you Doitis

  • Padraig McMahon says:

    DOMINDS🌘 Supernova deep in spaces boertx Domind Goin THOMAS MCMAHON UNKNOWN🌠 SLBART AIRES🌟Domind🌟○MA🇬🇷🔴RS●🌟Hobsphon AIRES 🌔Jess ware Jess Course ? don't how Jess Course Fraction Readership Question mark Course one Small Problems Jupiter Doitis🌔HOBSPHON Hack my Relationship and Friends Facebook Doitis Hacker Friends Doitis lier Friends

  • Padraig McMahon says:

    MA🌔🌟🔴🌟🌘RS Olampas V Joick♈ Because not KINGS👑 or Queens👑Know Jupiter Doitis kill off MA🔵RS Warter Because you Doitis Capcorin Doitis No AIRES Fack Doitis think GOD War not Fack Doitis look Farther my Course Childrens be with my Wife Jess Course AIRES Wift👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏👏BS👆Doitis Nuber One Sart Domin look copy my sart Sing AIRES wow Hahahahaha too Funny gast Joick🤖Doitis say Died me I am Voices💀😂🤪but not Died my Sart Sing in Supernova Deep in spaces boertx DOMINDS ○ ¿? me♈♠️🔥🔺️No Hero Thomas Because SPARTAN Joick McMahon same Greek people Because no GODS there need Tromfomrs moive give use Power withe he can Because Opinions Prinm donse Turst lier Humans might be Descends or Destroy Excite bay SPARTAN AIRES Friends with no AIRES no Learters just Opinions Prinm no body save you now till Died Bartter Crry Bartter Crry Hahaha No body save you now Bartter Crry Bartter Crry Hahaha Ooooooooo Save you now till Died porafisc worng ho Joick me right slfe 🇬🇷GRAECE and Reast World just me all AIRES people Slbart AIRES Orient AIRES SPARTAN and AIRES and Flivesss Girls🤪🤖🥰😡🌔🔺️🔥♠️♈♌♐ tures into sart Doitis🌟BS (🔥♈×♈🔥) look Fack KING👑Doitis lier pants on Fire

  • Joshua A. Kennedy says:

    We should terra form it first It was too small. No Magnetic core and very little atmosphere.

  • Suman Chatterjee says:

    No body
    Literally no body

    Phil : Mars was once very Wet… 😂

  • María Carla says:

    did you know that planets and Rihanna's albums are the same thing? go see my latest video to find out why 😀

  • Abondend Hope says:

    Maybe I missed this but I'm sure in school in science and on the Internet I was told mars does have water it's just frozen on the top of the planet like a North Pole?

  • Cameron Duncan says:

    It’s craz to think about the billions of complex and crazy planets in the universe with not a single living soul to appreciate them

  • Deep Singh says:

    I think b coz of all the sudden natural tragedy the ' Martian ' may have escaped to any other place may be titan

  • Athena Joy says:

    i dont get it, how can an atmosphere and an entire magnetic field just disappear?!
    Its like somebody or something just pressed delete….

  • usy 09 says:

    1:01 isn't Earth beautiful?

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