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Is there life on Mars?
More and more evidence seems to suggest the Red Planet could once support life
and it might still be habitable today.
I'm Sophie and welcome to The Countdown.
Life needs liquid water, which may have covered Mars billions of years ago.
Some of the earliest evidence came from orbiting satellites
which snapped photos of landscapes formed by water erosion.
When Curiosity arrived, more clues poured in.
In 2012, the rover discovered the signs of a stream bed,
proving a river once flowed through Gale crater.
More recently, it came across the remains of an ancient lake.
3.6 billion years ago, it was filled with fresh water
as well as chemicals that could have supported microbial life.
Also, when the Mars rover first used its drill to take a rock sample,
it found clay minerals.
These formed in slightly salty, but still drinkable liquid water.
Ancient Mars might actually have been a better place for life than our own planet.
According to geochemist, Steven Benner, life could have developed there first.
Billions of years ago, Mars had more oxygen and was dryer than Earth.
Benner thinks this was a better environment for developing molecules like RNA,
which are the building blocks of life.
In fact, Benner goes even further and suggests Martian molecules
might have seeded life on Earth.
Asteroid strikes could have hurled the molecules towards Earth on the backs of Martian rocks.
Although his theory is exciting, not everyone agrees.
The process that leads to RNA formation is still not entirely understood,
so these molecules could have developed independently in many locations.
If you don't like travel, look for Martian life here on Earth.
In 1996, NASA researchers claimed the meteorite ALH84001 contained evidence of ancient microbes.
This space rock formed on Mars 4 billion years ago, when the planet was still watery.
Samples from its interior contained the chemicals produced when microbes
digest and decay.
Even better, there were worm-like structures that looked like fossilized bacteria.
But this interpretation of the evidence could be wrong.
The features of the meteorite may have been formed by physical processes
rather than living creatures.
Mars may have been wet billions of years ago, but does it still have water today?
Absolutely.
According to Curiosity's analysis, two percent of the Martian soil
is made up of H20.
Unfortunately, the water is undrinkable because it's bonded to other minerals.
However, researchers have also noticed that in Spring and Summer,
dark streaks tend to appear, then lengthen on Martian slopes near the equator.
These marks may be due to the flow of salt water,
which would mean liquid water is abundant near the Marian surface.
Life is tough.
It can even survive in habitats that mimic modern Mars.
Several studies have placed microbial species in chambers
with low pressure, low temperature and a carbon dioxide atmosphere.
Most microbes can survive this simulated Martian environment.
They just lie dormant until they return to Earth-like conditions.
Certain species can even continue to function.
Which means organisms that survived NASA's cleaning processes
and hitched a ride to Mars, could now be living on the Red Planet.
Of course, they would have to deal with strong UV radiation and other obstacles,
but Mars may not be as inhospitable as we used to think.
I'm Sophie Bushwick and that's your countdown.
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And if you've got any topics you'd like to see in the future, let us know in the comments.