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Fifteen years ago, the Galileo spacecraft plunged into Jupiter’s atmosphere,
ending its eight-year mission studying the planet and its moons.
But that doesn’t mean it stopped sharing the system’s secrets.
As reported in a paper published this week in Nature Astronomy, researchers found something
new and surprising hiding in data Galileo captured all the way back in 1997:
evidence of water plumes on one of Jupiter’s moons, Europa!
According to a new computer model, while you were breaking in your Nintendo 64,
this spacecraft might’ve been quietly observing water on another world.
If plumes on Europa sounds familiar, it might be because there’s another moon with
water plumes whose name also starts with an ‘E’: Enceladus.
It orbits Saturn, and we’ve talked about it here before.
Europa is about six times bigger though, around the same size as our Moon, and data suggest
it has twice as much water as the Earth does.
It’s enough for a global, underground ocean,
but we’ve never actually had definitive proof that it’s down there.
To do that, well, we’d need to find something like plumes.
As early as 2012, we had some hints from the Hubble Space Telescope that they might exist,
and we’ve compiled even more evidence over the years.
But because all these measurements were done at the very limit of Hubble’s sensitivity,
their accuracy is debated.
To solve this mystery, we need better data, ideally, something closer to the source.
Unfortunately, Juno, our spacecraft currently orbiting Jupiter,
doesn’t have the equipment to study these features.
In fact, it was launched before any evidence of plumes had been discovered.
So we can’t give the local help a side quest.
The good news though, is we had our old friend Galileo!
Likely inspired by those Hubble discoveries,
a team of astronomers recently gave the 20-year-old data another look.
And we’re glad they did.
During its flyby of Europa, Galileo got as close as 206 kilometers from the moon’s surface,
and it measured changes in Europa’s magnetic field strength and distribution of plasma.
Now, we think those changes could easily be explained by the presence of a plume,
one maybe around 1000 kilometers wide and at least 200 kilometers tall.
At least that’s what the team’s computer models suggest.
And if this turns out to be true, it would be a huge bonus for space exploration.
After all, it means that if we sent a mission to Europa, we’d be able to sample its oceans
without drilling through kilometers of ice.
But this is only one model, so we’ll need more evidence to be sure.
And ultimately, our best chance of confirming Europa’s plumes is still sending a craft
back to Jupiter that’s capable of detecting them.
Which, of course, astronomers are already working on.
NASA’s Europa Clipper mission is slated to launch in the 2020s,
and it’ll have nine instruments to help study the plumes’ composition, like a mass spectrometer.
There may also be a lander in the works, if it gets the funding.
And an ESA mission dubbed JUICE should launch in 2022.
When it reaches Jupiter around 2030, it’ll study Europa, as well as two of Jupiter’s
other moons astronomers believe have some liquid water under their surfaces:
Ganymede and Callisto.
So, we’ll just have to wait and see.
Meanwhile, here’s some news we had to wait over 13 billion years to see,
light from some of the very first stars in the universe.
A paper published in Nature this week reports the discovery of stars forming in a
distant galaxy as early as 250 million years after the Big Bang,
when the universe was only 2% its current age.
Using an array of radio telescopes called ALMA, an international team of astronomers
was able to analyze the light coming from stars in the galaxy dubbed MACS1149-JD1.
Based on how fast the galaxy is moving away from us, they estimated its light to be about
13.3 billion years old; only 500 million years younger than the universe itself.
They could make this estimate because the universe is expanding, so galaxies farther
away, and therefore older, are moving away from us faster than the ones nearby.
And we can detect those speeds based on what the light from these galaxies looks like.
Of course, if the galaxy has light, it probably means it has stars, too.
And since they couldn’t just suddenly pop into existence, it means they have to be even
older than 13.3 billion years.
The researchers figured out their age by modeling when early bursts of star formation
had to have happened in order to make the galaxy’s light signature,
also called its spectra, match their data.
They found there had to be a bunch of stars forming around 300 million years
prior to the light we’re seeing now.
And that means most of the stars themselves, and therefore the galaxy as a whole,
was forming only 250 million years after the universe came to be.
Besides being cool to know about, this discovery is good news for anyone trying to study the
universe’s first generation of stars, because it suggests we have the tools to study them.
We can figure out exactly when they started forming and what properties they have.
And this is especially good news for one future mission: NASA’s James Webb Space Telescope,
which is designed to study the early universe.
So when it finally launches, it looks like it has yet another target to train its sights on.
All it has to do now is go to space.
Clearly, a lot of astronomy involves waiting.
Thanks for watching this episode of SciShow Space!
If you can’t wait for the next space news episode, it’s okay: We have plenty of other
stuff for you to learn about, like what would happen if the universe were shaped like a donut.
Because this is a thing astronomers think about.
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