Learn about the science behind the current exploration of the solar system in this free class. Use principles from physics, chemistry, biology, and geology to understand the latest from Mars, comprehend the outer solar system, ponder planets outside our solar system, and search for habitability in our neighborhood and beyond. This course is generally taught at an advanced level assuming a prior knowledge of undergraduate math and physics, but the majority of the concepts and lectures can be understood without these prerequisites. The quizzes and final exam are designed to make you think critically about the material you have learned rather than to simply make you memorize facts. The class is expected to be challenging but rewarding.
Lecture 1.07: The first missions to Mars
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En provenance du cours de Caltech
The Science of the Solar System
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À partir de la leçon
Unit 1: Water on Mars (week 1)
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Mike BrownProfessor
Planetary Astronomy
The first mission to Mars was launched in October of 1960, by the Soviet Union.
In fact, two identical spacecraft that looked like this were launched
in October of 1960, with the goal of flying by Mars,
something like eight and a half months later.
Neither one of them made it even into Earth's orbit.
They both went up.
The rockets on which they were in both went up,
and the third stage failed to ignite.
They fell back down to Earth.
In 1962, the next time that Earth and Mars were configured so
that we could go from one to the other with that minimum energy configuration,
the Soviet Union launched two more.
We call those Mars 1962A and 1962B.
The, the official names from the Soviets were never released.
Neither one made it out of Earth orbit.
Mars 1962B was particularly ambitious.
It was supposed to not just fly by Mars, it was supposed to land on Mars.
The first thing launched that was supposed to land on another planet.
It didn't. Another Soviet spacecraft was launched
toward Mars in 1962.
And this one made it into Earth's orbit.
It made it out of Earth's orbit, and remember as we've said, once you make it
out of Earth's orbit, that's actually where the easy part commences.
So, it's on its way to Mars.
It's on its coast phase to Mars, radioing back to the Earth every once in a while,
and radio communications were lost.
The assumption being that somehow the spacecraft got pointed in the wrong
direction, and can no longer communicate with the Earth.
If it was on the right trajectory though, it did actually fly by Mars,
or maybe even hit Mars we'll never know.
Just for a complete list, the Soviet Union tried again in 1964 with two probes,
both lost.
Tried again in 1969 with two probes, both lost.
So, okay, I said it's relatively easy to get there.
A lot of these losses occurred in the part where you're going through the atmosphere,
the hard part of it.
And the other parts were, well yes, it is easy to get to Mars, but
it is actually kind of hard to have your spacecraft still be alive and
talking to you when it gets there.
Many of these spacecraft, again, probably did actually make it to Mars.
In 1964, when the Soviets had sent two failed missions to Mars,
the United States also attempted their first missions to Mars.
They did the same approach, send two identical things, hope that one works.
The first one failed.
It failed when the shroud that protects the spacecraft as it's going up on
the first rocket failed to open.
Spacecraft never came alive.
Fell back down in the ocean.
Dead.
The second one made it.
Mariner IV was the first spacecraft to fly past Mars, and
it flew past Mars on July 14, 1965.
It had, by today's standards, some pretty primitive instruments.
It had basically a television camera that it transmitted very,
very slowly back to the Earth.
But, it allowed the first images of a planet other than the Earth,
to be seen up close.
Here's what some of them looked like.
Okay, there it is.
This is the first image ever returned from another planet.
And, okay yeah,
it's really kind of crummy, because we're used to really fabulous things these days.
But, just imagine, this is, you're suddenly looking at Mars, this thing that,
for the entire history of the universe, had only been a little red dot in the sky.
And then,
a slightly larger object that you could vaguely make out surface features on.
And now, it's a real body.
You can see it's got a real size, a real shape.
You can't really see anything on the surface on this very,
very first image that came out.
You can, though, see the atmosphere.
This, this stuff you see over here is actually
the atmosphere of Mars that you're actually seeing.
The rest of it is just the surface.
There were only a few images that got transmitted back,
the spacecraft went zipping on by and the transmissions were so
slow that it only had time to send back a few.
Let me show you a couple of the other ones.
Here are two of the highest resolution images that were obtained, and
when you look at them, they look a little bit familiar.
They look familiar if you've been looking at the moon.
What do you see?
Well, all you really see are impact craters, crater, crater, crater,
rims of craters, degraded craters that have been around for maybe a long time.
Over here, an old crater that's been sort of crumbling,
new craters, craters everywhere.
Craters everywhere makes Mars look a lot like the moon.
Mars is, in these pictures, a dry,
dead and I hate to say it, but pretty uninteresting place.
Why do I say boring?
Well, the Earth is interesting, interesting to us in many ways.
But one of the things that's interesting about it is that water cycle,
is the fact that we have rain, that we have things happening on
the surface other than just, you know, meteorites hitting us.
That happens every once in a while, too.
The moon is really much less interesting that way.
The surface is old, it's cratered, it's rocky.
If you make a crater on the moon, it really just sticks around for a long time.
If you make a crater on the Earth, it doesn't stick around for very long.
There are a couple famous craters that you can go find on the Earth,
one of the best ones being fairly close to me, out in Arizona, Meteor Crater.
But most of the Earth doesn't have craters and that's because things like rain and
plate tectonics and lakes and oceans, have eroded any of the craters away.
That's what I mean by interesting.
Mars looks like the moon.
It looks like it's been sitting there, dead, for
most the history of the solar system, just being pummeled by rocks.
As exciting as these first images of Mars were,
I, I suspect that to many people, they were quite a disappointment.
Even if we knew there were no canals.
Even if we knew there were probably not beings living on there.
Even if by now, we were figuring out that, that water was not on the surface,
it was too cold, it would be frozen.
Looking at this, it's pretty clear that not only is Mars cold and
desert-like and frozen, it's been that way forever.
The good news, though, is that's not actually true.
Because there were so
few images sent back from that Mariner IV spacecraft, we just got unlucky.
There are parts of Mars that really have had no interesting activity,
no, no rainfall, no water, no anything for most of the history of Mars.
Those are generally in the southern highlands of Mars.
We'll talk a lot more about the geology of Mars as the lectures go on.
But if you, if you only look at the southern highlands of Mars, it does look
a lot like the moon, but there are places on Mars where you could have looked,
where you would have seen a very different story.
And even when you look at the highlands of Mars
you see some things that are not precisely moon-like.
I showed you, for example, these craters.
These craters are not as distinct as these smaller craters.
And what they look like is that they have been eroded.
They haven't eroded away completely.
They certainly haven't eroded away as much as they would have on the Earth.
But there's a hint even from these very first images, that perhaps Mars is not
entirely moon-like, and something more interesting might be going on.
We'll see some dramatic evidence that, that's true over the next few lectures.
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