WEBVTT FILE

1
00:00:00.010 --> 00:00:12.130
[ music ]

2
00:00:12.150 --> 00:00:19.980
When you take a look at Mars, you probably wouldn't think that it looks like a very nice place to live: it's dry, it's dusty, and there's practically no atmosphere.

3
00:00:20.000 --> 00:00:23.980
But some scientists think that Mars may have once looked like a much nicer place to live,

4
00:00:24.000 --> 00:00:29.180
with a thicker atmosphere, cloudy skies, and possibly even liquid water flowing over the surface.

5
00:00:29.200 --> 00:00:33.330
So how do you go from something like this...to something like this?

6
00:00:33.350 --> 00:00:41.330
NASA's MAVEN spacecraft will give us a clearer idea of how Mars lost its atmosphere, and scientists think that several processes have had an impact.

7
00:00:41.350 --> 00:00:48.030
One of these processes is called Sputtering, where atoms are knocked away from the atmosphere due to impacts from energetic particles.

8
00:00:48.050 --> 00:00:52.130
In our solar system, the Sun constantly emits high-energy photons.

9
00:00:52.150 --> 00:00:59.350
When one of these photons enters the atmosphere of a planet, it can crash into a molecule, knocking loose an electron and turning it into an ion.

10
00:00:59.370 --> 00:01:05.380
Ions by themselves don't do much, but when a magnetic field is nearby they'll spin around the field.

11
00:01:05.400 --> 00:01:10.680
Conveniently, the Sun generates a giant magnetic field that is carried by the solar wind.

12
00:01:10.700 --> 00:01:15.230
As the magnetic field sweeps past the planet, some ions will get carried away.

13
00:01:15.250 --> 00:01:20.640
Other ions, depending on where they form, won't get carried away but will hit the top of the atmosphere.

14
00:01:20.660 --> 00:01:26.500
These ions can then crash into other molecules and fling atoms everywhere, like a cue ball in a game of pool.

15
00:01:26.520 --> 00:01:31.730
Some of these atoms can be knocked, or sputtered, into space, causing atmospheric loss,

16
00:01:31.750 --> 00:01:35.080
and over billions of years this could have caused quite a bit of change,

17
00:01:35.100 --> 00:01:40.230
especially since the solar wind may have been more intense early in our solar system's history.

18
00:01:40.250 --> 00:01:44.700
Scientists think that all of this may have caused Mars to gradually transform

19
00:01:44.720 --> 00:01:49.780
from what may have been a very nice place to live, into the dry, dusty world we know today,

20
00:01:49.800 --> 00:01:56.880
and MAVEN will study this process and tell us how it really works.

21
00:01:56.900 --> 00:02:08.175
[ music, satellite beeping ]