Name: Why Mars Died, and Earth Lived
Uploaded: 2013-12-09T15:47:46.000Z
Duration: 9 min 33 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

The Mars rover, Curiosity, is the latest in a long line of missions to Mars…

Landers sent to scoop its soil and study its rocks, orbiters sent to map its valleys and

Did liquid water once flow on this dry and dusty world? Did it support life in any form?

The science that comes out of these missions may help answer a much larger, more philosophical

Is our planet Earth the norm, in a galaxy run through with life-bearing planets?

Or is Earth a rare gem, with a unique make-up and history that allowed it to give rise to

On Mars, Curiosity has spotted pebbles and other rocks commonly associated with flowing

It found them down stream on what appears to be an ancient river fan, where water flowed

This shows that at some point in the past, Mars had an atmosphere, cloudy skies, and

So what could have turned it into the desolate world we know today?

One process that very likely played a role goes by the unscientific name, “sputtering.”

Like the other planets in our solar system, Mars is lashed by high-energy photons from

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.

The solar wind brings something else: a giant magnetic field.

When part of the field grazes the planet, it can attract ions and launch them out into

Another part might fling ions right into the atmosphere at up to a thousand kilometers

The ions crash into other molecules, sending them in all directions like balls in a game

Over billions of years, this process could have literally stripped Mars of its atmosphere,

especially in the early life of the solar system when the solar wind was more intense

Sputtering has actually been spotted directly on another dead planet, Venus.

The Venus Express mission found that solar winds are steadily stripping off lighter molecules

They escape the planet on the night side, then ride solar breezes on out into space.

This process has left Venus with an atmosphere dominated by carbon dioxide gas, a heat trapping

compound that has helped send surface temperatures up to around 400 degrees Celsius.

The loss of Venus’ atmosphere likely took place over millions of years, especially during

solar outbursts known as coronal mass ejections.

If these massive blast waves stripped Venus and Mars of an atmosphere capable of supporting

life… how did Earth avoid the same grim fate?

We can see the answer as the solar storm approaches earth.

  Our planet has what Mars and Venus lack - a

powerful magnetic field generated deep within its core.

  This protective shield deflects many of the

high-energy particles launched by the Sun.

In fact, that’s just our first line of defense.  

Much of the solar energy that gets through is reflected back to space by clouds, ice,

The energy that earth absorbs is just enough to power a remarkable planetary engine: the

It’s set in motion by the uneveness of solar heating, due in part to the cycles of day

and night, and the seasons. That causes warm, tropical winds to blow toward the poles, and

Wind currents drive surface ocean currents.  

This computer simulation shows the Gulf Stream winding its way along the coast of North America.

This great ocean river carries enough heat energy to power the industrial world a hundred

It breaks down in massive whirlpools that spread warm tropical waters over northern

seas. Below the surface, they mix with cold deep currents that swirl around undersea ledges

Earth’s climate engine has countless moving parts: tides and terrain, cross winds and

currents -- all working to equalize temperatures around the globe.

Over time, earth developed a carbon cycle and an effective means of regulating green

In our galaxy, are still-born worlds like Mars the norm?

Or in Earth, has Nature crafted a prototype for its greatest experiment: Life?