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In the past, the main way we’ve studied the Sun
is by examining its light, and it gives off a lot of it.
But the Sun also gives off particles:
high-energy, charged matter that it spits out in huge bursts.
And those are harder to study, because Earth’s magnetic field deflects them,
which is great for keeping us alive, but also kind of a bummer for science,
because there’s so much they could tell us about our star.
As tricky as it is, though,
scientists have found ways to study physical particles from the Sun in the past,
and they’ve helped us understand things like the Sun’s history, composition,
and the threat it poses to future explorers.
As soon as you get past the Earth’s magnetic field, it gets a lot easier to sample solar matter,
because it’s constantly streaming out into the solar system in what’s called the solar wind.
So, when NASA scientists were gearing up for Apollo 11,
they realized they had the chance to sample the Moon and the Sun at the same time.
They equipped the Apollo astronauts with a very fancy tool
for collecting solar particles: a big sheet of aluminum foil.
And while they were bouncing around on the moon,
Neil Armstrong and Buzz Aldrin stuck what kind of looked like an aluminum foil flag
in the ground, with the surface of the sheet facing the Sun.
As ions in the solar wind hit the foil, those with enough energy embedded themselves in the material.
The astronauts took the foil home with them, and back on Earth,
scientists found helium, neon, and argon nestled in the aluminum.
Now, people already had a pretty good idea that these elements were present in the solar wind,
but this was the first time scientists were able to directly confirm that.
Astronauts repeated this experiment on each Apollo mission,
and over time, they found that they could actually tell
how strong the solar wind was based on the amount of helium in each experiment.
So those experiments were intriguing, but they were also short and limited,
and these were the last samples we had of solar wind for a long time.
That changed in 2001, when NASA launched the Genesis mission,
the first mission with the specific goal of collecting samples from the Sun.
This time, instead of parking a detector on the Moon,
NASA launched a spacecraft into the first Lagrange point, or L1,
between the Earth and the Sun.
Lagrange points are basically gravitational sweet spots between two big objects,
where a smaller object can safely orbit without being pulled one way or another.
The spacecraft stayed up there for two-and-a-half years,
with its sample collector exposed to solar wind, drinking up ions.
At the end of the mission, the whole spacecraft flew back over to Earth,
where a canister holding the sample collectors detached itself
and plunged back to the ground.
Now, that didn’t go perfectly:
The parachutes failed to deploy, and the capsule crashed-landed in the Utah desert.
Sadly, that destroyed many of the samples, but not all of them!
And we learned some pretty revolutionary stuff from the ones that survived.
Like, it turns out that the atoms making up the Sun
have different masses than the atoms that make up Earth.
And that’s surprising, because as far as we can tell,
both the Sun and the Earth formed out of the same disk of dust and gas.
So we’d expect them to have the same building blocks.
But that’s not what scientists found.
For example, Earth has a higher fraction of heavy oxygen,
or oxygen atoms with an extra neutron or two, compared to the Sun.
And we don’t really know why that is.
There are a few hypotheses.
Like, it’s possible that, right after the Sun formed,
UV radiation redistributed some of the heavy oxygen in the disk
and that the Earth formed in an area with heavier oxygen.
It’s still an open mystery, though, and one we’d probably not even know about
without examining actual pieces of the Sun!
As useful as they are, we don’t just study solar particles to understand the Sun;
we also do it to understand how they affect other planets,
and how they’d potentially interact with living things.
And that’s why scientists have also been interested in
studying the solar particles that make it to Mars.
Like the Moon, Mars has no global magnetic field,
so some particles from the solar wind make it to the surface.
And we’re going to Mars all the time, so why not gather solar particles while we’re at it?
NASA’s Curiosity rover has actually helped us out with that.
It has an instrument called the Radiation Assessment Detector,
which was mainly intended to help scientists assess
how much radiation astronauts should prepare for en route to Mars.
But when solar activity is strong enough,
it sometimes picks up charged particles on the surface of Mars.
And it’s been able to tell us some interesting things,
like what kind of radiation any past life might have been up against,
or what future human explorers could have to deal with.
For instance, it found that, while Mars’ thin atmosphere
shields the surface from lower-energy particles,
the high-energy helium ions and protons just punch right through.
And those high-energy particles would mess up the DNA
of just about anything living on the surface.
But organisms could potentially survive a few meters underground.
This radiation wouldn’t just mess with living things,
though, even if there were life somewhere, at some point,
these high-energy particles could mess with the evidence, too.
They react with the chemicals in rocks,
so they could alter any organic molecules left over from living things.
But it’s not all bad news; just knowing that is useful!
Because we know that products of those reactions are compounds
called organic salts, so we can look for them as clues to past life,
in addition to looking for other stuff like amino acids.
It’s taken some serious creativity to study particles from the Sun
from our well-shielded planet, but we learned a lot from these three missions.
And the best is still to come!
In 2018, NASA launched its Parker Solar Probe on an incredible mission:
to touch the corona and analyze the Sun’s matter straight from the source.
It’s on track to get there by 2024,
so in the next few years, there’ll be way more to discover.
Thanks for watching this episode of SciShow Space!
And thanks especially to the patrons who support us on Patreon.
It takes a big team to make a SciShow video,
and we couldn’t make episodes like this without your help.
If you’re not yet a patron but want to support what we do,
you can find out more at patreon.com/SciShow.
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