In the last few years, there’s been a lot of talk about a mission to fly by Jupiter’s
moon Europa -- and last week, NASA proposed a follow-up mission to land on its surface.
All this talk about Europa has been for good reason.
Under its surface is an ocean containing three times as much water as the entire Earth, which
makes it a great candidate for finding extraterrestrial life.
But before we land, the Europa Multiple Flyby Mission will check it out first.
The probe, which should launch in the early 2020s, will fly by Europa 45 times and collect
data on its composition and surface.
Then, if this new lander gets approved, it’ll launch in 2024 or 2025.
The lander’s main goal will be to determine if there is or ever was life on Europa, and
it’ll do that by digging around 10 centimeters below the surface and take at least five samples.
Then, using a microscope on board, the lander will analyze those samples, looking for tiny
cells or any sign that life may have once existed on the moon.
According to NASA, the lander’s microscope will be so precise that it can identify cells
as small as 0.2 microns in diameter — that’s two ten-millionths of a meter!
It’s important to take underground samples because Jupiter gives off a lot of extreme
radiation, so life probably wouldn’t have evolved on the surface.
We wouldn’t be able to get these samples from just a flyby mission, so landing on Europa
is the only way to get the full picture.
But even if it doesn’t find signs of life, the lander will also study whether life has
the potential to evolve -- in other words, if Europa could be habitable at all, based
on factors like the depth of underground water and the chemistry of the samples.
Finally, the lander’s third goal will be to gather information for future exploration
and match up data on the ground and data from the flyby mission.
And all of this will have to happen in less than three weeks!
The scientific instruments onboard the lander will live inside a compartment called a radiation
vault, but they’ll still be really sensitive.
And Jupiter’s radiation is so strong that the instruments will only be able to last
about twenty days on the surface before they break down.
There’s still a lot of work to be done on this mission before it’s approved for development,
but if that happens, you can look forward to three intense weeks of science around 2030!
And speaking of life elsewhere in the universe, you might have heard last year about a rocky,
Earth-sized planet called Proxima b.
Proxima b, which orbits our closest neighboring star, Proxima Centauri, is only four light
years away, and astronomers think it’s located in the star’s habitable zone.
In other words, Proxima b is just the right distance from its star to have liquid water
and relatively mild temperatures.
When the discovery was announced, it make a lot of people -- including us here at SciShow
-- really excited, because it was the first time we’d found a planet so close to Earth
so that could potentially be habitable.
...but all good things must come to an end.
It turns out that Proxima b isn’t habitable after all, according to a study published
in The Astrophysical Journal Letters last week.
The problems have to do with its star, Proxima Centauri, which is a red dwarf.
Proxima b’s orbit is really close to the star -- about 10 to 20 times closer than we
are to the sun.
Red dwarfs are smaller and colder than our sun, so the planet’s close orbit puts it
right in the sweet spot where liquid water — and therefore life — could potentially exist.
Unfortunately, though, red dwarfs are also really active, and they can shoot out deadly
superflares of X-ray and ultraviolet radiation -- right into the habitable zone.
Now, with a strong atmosphere and magnetic field, it’s possible the radiation wouldn’t
be too much of an issue.
But when the researchers modeled planets around red dwarfs, taking the stars’ radiation
into account, they found that the superflares can actually strip the electrons off of molecules
in a planet’s atmosphere.
Then, those molecules -- which can include oxygen, hydrogen, and nitrogen -- easily get
dragged out into space, which is bad news if life is trying to evolve.
Not only are these elements the building blocks of life as we know it, but hydrogen and oxygen
also make up water.
So if there’s no water in the atmosphere, there probably isn’t any on the surface, either.
The researchers found that a young red dwarf star could make its planets uninhabitable
within less than a hundred million years, which is much less time than it would take
for life to develop.
So, it looks like we won’t be visiting our neighbors on Proxima b any time soon.
But even though it crushed our hopes and dreams, this research is also helping astronomers
redefine the definition of a habitable zone around a red dwarf.
They used to only include factors like temperature, but now they can start including radiation, too.
And even if there’s no hope for life on Proxima b, maybe in a decade or two we’ll
find something a little closer to home if the Europa lander works out.
We’ll just have to wait and see!
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