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Life on Mars?

  • Teacher Resource
  • Posted 05.08.12
  • NOVA

In this video excerpt from NOVA, learn about the discovery of water ice on Mars. Satellites analyzing radar waves bouncing back from Mars's polar caps reveal that if it all melted, there is enough water ice to cover the entire planet in an ocean more than 80 feet deep. However, just like a piece of dry ice on Earth goes directly from solid ice to vapor without forming a liquid, water ice on Mars behaves the same way because the pressure is so low. In activity six from the education collection that accompanies this video, students identify the top candidates for life in the solar system.

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Supplemental Media Available: Education Collection (Document)

NOVA Life on Mars?
  • Media Type: Video
  • Running Time: 2m 59s
  • Size: 10.6 MB
  • Level: Grades 6-12

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This media asset was excerpted from NOVA: "Finding Life Beyond Earth."

Questions for Discussion

    • What evidence on Mars suggests that water once flowed on the surface?
    • How does water ice behave on Mars and why?
    • Could life exist on Mars without liquid water on the surface? Why?


NARRATOR: But what about Mars?

Organic compounds have yet to be found here, but scientists are searching the planet for the other preconditions of life.

There have been many missions to Mars and nearly all suggest that water once flowed on the surface. These detailed images from satellites orbiting Mars reveal vast canyons blasted out by epic floods and valleys carved by raging rivers. But the evidence indicates that all this water disappeared from the surface billions of years ago, as Mars cooled down and lost its atmosphere.

But on May 25, 2008, a spacecraft called Phoenix touches down near Mars' north pole. Digging a few inches down, it exposes a white material that vaporizes after a few days.

Soil analysis reveals it is water ice.

NARRATOR: Satellites analyze radar waves bouncing back from both polar caps. They reveal that beneath a layer of frozen carbon dioxide there is a lot of water ice. If it all melted, it would cover the whole planet in an ocean more than 80 feet deep.

NARRATOR: The same satellites orbiting Mars are discovering that buried ice is also widespread beneath the desert floors.

CHRIS MCKAY (ASTROBIOLOGIST, NASA AMES RESEARCH CENTER): When we look at Mars, we see what looks like a desert world, with no water, but, in fact, Mars has lots of water. It's ice; Mars is an ice cube covered with a layer of dirt.

NARRATOR: But this doesn't mean that finding life here is imminent. Ice doesn't melt the same way on Mars as it does on Earth. The atmospheric pressure here is 150 times lower than ours. It's impossible for water to exist as a liquid at the surface.

CHRIS MCKAY: Ice on Mars behaves like dry ice does on Earth. A piece of dry ice, on Earth, goes directly from the solid ice to vapor. It doesn't form a liquid. That's why we call it dry ice.

On Mars, the pressure is so low that water ice does the same thing.

NARRATOR: No liquid water on the surface of Mars today means that vital chemical reactions cannot take place. It seems impossible that life could exist there. But could it exist in the buried ice itself?

Resource Produced by:

					WGBH Educational Foundation

Collection Developed by:

						WGBH Educational Foundation

Collection Funded by:


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