00:00:49
The Mars rover, Curiosity, is the latest in
a long line of missions to Mars…
00:01:03
Landers sent to scoop its soil and study its
rocks, orbiters sent to map its valleys and
00:01:13
They are all asking the same question.
00:01:18
Did liquid water once flow on this dry and
dusty world? Did it support life in any form?
00:01:29
And are there remnants left to find?
00:01:35
The science that comes out of these missions
may help answer a much larger, more philosophical
00:01:46
Is our planet Earth the norm, in a galaxy
run through with life-bearing planets?
00:01:57
Or is Earth a rare gem, with a unique make-up
and history that allowed it to give rise to
00:02:06
On Mars, Curiosity has spotted pebbles and
other rocks commonly associated with flowing
00:02:21
It found them down stream on what appears
to be an ancient river fan, where water flowed
00:02:26
down into Gale Crater.
00:02:32
This shows that at some point in the past,
Mars had an atmosphere, cloudy skies, and
00:02:39
liquid water flowing.
00:02:47
So what could have turned it into the desolate
world we know today?
00:02:55
One process that very likely played a role
goes by the unscientific name, “sputtering.”
00:03:08
Like the other planets in our solar system,
Mars is lashed by high-energy photons from
00:03:21
When one of these photons enters the atmosphere
of a planet, it can crash into a molecule,
00:03:28
knocking loose an electron and turning it
into an ion.
00:03:36
The solar wind brings something else: a giant
magnetic field.
00:03:43
When part of the field grazes the planet,
it can attract ions and launch them out into
00:03:56
Another part might fling ions right into the
atmosphere at up to a thousand kilometers
00:04:05
The ions crash into other molecules, sending
them in all directions like balls in a game
00:04:15
Over billions of years, this process could
have literally stripped Mars of its atmosphere,
00:04:22
especially in the early life of the solar
system when the solar wind was more intense
00:04:27
than it is today.
00:04:32
Sputtering has actually been spotted directly
on another dead planet, Venus.
00:04:40
The Venus Express mission found that solar
winds are steadily stripping off lighter molecules
00:04:48
of hydrogen and oxygen.
00:04:52
They escape the planet on the night side,
then ride solar breezes on out into space.
00:05:01
This process has left Venus with an atmosphere
dominated by carbon dioxide gas, a heat trapping
00:05:11
compound that has helped send surface temperatures
up to around 400 degrees Celsius.
00:05:25
The loss of Venus’ atmosphere likely took
place over millions of years, especially during
00:05:31
solar outbursts known as coronal mass ejections.
00:05:39
If these massive blast waves stripped Venus
and Mars of an atmosphere capable of supporting
00:05:45
life… how did Earth avoid the same grim
fate?
00:05:54
We can see the answer as the solar storm approaches
earth.
00:06:03
Our planet has what Mars and Venus lack - a
00:06:07
powerful magnetic field generated deep within
its core.
00:06:13
This protective shield deflects many of the
00:06:16
high-energy particles launched by the Sun.
00:06:23
In fact, that’s just our first line of defense.
00:06:28
Much of the solar energy that gets through
is reflected back to space by clouds, ice,
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