Landing on Mars is easier said than done.
Over the last 50 years, spacecraft have landed
on more than half a dozen worlds including Venus,
Saturn's moon Titan, a comet, and more.
But nowhere has proven more treacherous
than the Red Planet, Mars. To date, only 40%
of attempted landings have been successful.
But just looking at it, Mars seems pretty harmless, right?
It doesn't have toxic clouds like Venus
and there's plenty of flat, stable places to land.
Unlike a comet.
But here's the thing.
It's not what you can see that's the problem.
It's what you can't.
It's the atmosphere.
Mars' atmosphere is 100 times thinner than Earth's.
Because Mars' atmosphere is so thin,
it makes parachutes less effective.
10 times less effective, in fact.
So let's say you can skydive on Mars.
And let's use the same-sized parachute as one
you would use on Earth.
On Earth, skydivers' chutes slow them down
to about 20 miles per hour.
But on Mars, even with a parachute,
you would still be falling at 200 miles per hour.
Which, obviously is not good.
Now you could make your parachute larger
and slow down even more and that's partly what NASA does.
For example, its Curiosity rover used the largest
supersonic parachute at the time when it landed in 2012.
But even that couldn't slow Curiosity down enough.
To see why let's go back to the skydive.
If you wanted to slow down at the same landing speed on Mars
as on Earth, you would need a parachute
that's 10 times wider.
Or about 110 feet in diameter.
Wide enough to cover the length
of two and half school buses.
Now here's the catch.
NASA's Curiosity rover weighs about 13 times more
than the average person.
Which means to slow down at the same speed,
it would need an even bigger chute.
One that is about, oh boy, 400 feet in diameter.
But in reality,
Curiosity's parachute was nowhere near that size.
It was only 70 feet in diameter.
Why?
Because the bigger the chute gets,
the greater chance it will rip.
In fact, the largest parachute ever built and tested
was just 150 feet wide.
So in the end,
it's physically impossible to build a parachute big enough.
Which makes landing on Mars risky at best.
So how do space agencies do it?
Well, very carefully.
First, the spacecraft deploys a giant parachute to slow down
as much as possible.
Usually around 200 miles per hour.
Then, it fires retrorockets to take it the rest of the way
and that might not sound so hard but if the parachute
doesn't deploy at just the right time,
or the rockets don't fire at just the right height,
it's all over.
To date only three space agencies
have ever tried to land on Mars.
NASA, the European Space Agency,
and the former Soviet Union.
None have a perfect record.
So if landing on Mars is so hard,
why do we keep doing it in the first place?
Besides the moon, Mars has more artificial instruments
on and around it than anywhere else in our solar system.
And you could say that's because Mars is close by
or that it might be the best spot to search for signs
of alien life.
Or it could be that with each successful new landing,
we come one step closer to the grandest ambition of all.
To become the first species ever
to inhabit a world beyond our own.