In December NASA announced that it had narrowed down its potential list of planetary science
missions to two.
There's the Comet Astrobiology Exploration Sample Return (or CAESAR), a mission that
would return to Rosetta's Comet 67P and bring a sample back to Earth.
And then there's Dragonfly, a nuclear-powered helicopter that would buzz around in the atmosphere
of Saturn's moon Titan, exploring this fascinating world.
Sadly, there can only be one mission.
And so, NASA will let both missions continue working out the details until the final decision
can be made in mid-2019.
And if all goes well, the chosen mission will set off in middle of the 2020s.
Comet sample return or Titan helicopter, which one will it be?
In order to help out NASA with their decision making process, I've teamed up with Tim
Dodd, the Everyday Astronaut, to advocate for each of the missions.
I'm going to do everything I can to convince you that a comet sample return mission makes
the most sense, while Tim's going to advocate for the Titan Dragonfly.
And then, in the end, we'll give you a poll where you can vote.
We'll pass along the vote to the decision makers, and I'm sure they'll dismiss it
for the hilarious, and unhelpful YouTube stunt that it is.
Phew, I've got
to
advocate AGAINST a nuclear-powered helicopter on Titan.
Okay… here goes.
Comets are some of the most important objects of study in the Solar System.
They're relics, frozen in time from the earliest moments of our Solar System's history.
It's believed they delivered water and organic materials to the newly forming Earth, and
could have been pivotal to our understanding of how life first got started, billions of
years ago.
It's not surprising that they've been a target for several space missions.
The first mission to reach a comet was in 1985, when the International Comet Explorer
passed within 8,000 kilometers of Comet Giacobini-Zinner.
Other missions got even closer, like ESA's Giotto, which came within 200 kilometres of
Comet Grigg-Skjellerup in 1992.
NASA's Stardust mission passed through the tail of Comet Wild 2 in 2004, and brought
samples back to Earth for study.
NASA's Deep Impact smashed into Comet Tempel 1 in 2005, gouging out a crater, revealing
the comet's interior to a partner spacecraft.
But the one you're most familiar with was the European Space Agency's Rosetta Mission,
launched back in 2004 to perform the detailed study of Comet 67P/Churyumov-Gerasimenko.
Not only would it go into orbit, but it would try to land a separate spacecraft down on
the surface of the comet.
On August 6th, 2014, Rosetta arrived at the comet, and a few months later, it deployed
its Philae lander in an attempt to sample the surface.
The orbiter did great, returning high-resolution images of the surface of the comet.
The lander, not so much.
Its harpoons failed to fire, and it bounced gently a couple of times off the soft surface
of 67P, eventually coming to rest on its side.
Even if Philae had been successful, and been able to send back detailed information about
the surface of the nucleus of a comet, there's only so much it could do.
The next step in this journey to understanding comets, and helping them unlock the secrets
of the early Solar System is to bring a sample back to Earth.
Planetary scientists need to get their hands on a chunk of cometary nucleus, here on Earth,
where they can run it through every experiment and mass spectrometer they can get their hands
on.
We're entering the age of sample returns.
We've got Moon rocks from the Apollo missions, OSIRIS-REx is on its way to Asteroid Bennu
to bring us home a spacerock, missions are in the works to bring a sample back from Mars.
We need a chunk of a comet.
Dr. Steve Squyres, the principle investigator of NASA's Spirit and Opportunity Rovers
is back with a new mission: Comet Astrobiology Exploration Sample Return (or CAESAR).
Its purpose will be to fly to 67P, send a lander down to the surface, retrieve a sample
in a pristine, comet-like state, and bring it back to Earth.
When the sample returns to Earth, planetary scientists will be able to open it up, gases
and all, and study the comet to their heart's content, from the comfort of their earthly
laboratories.
The ESA scientists chose 67P as a target for a good reason.
In 1959, the comet had a close flyby with Jupiter, changing its orbit to send it closer
to the inner Solar System.
For at least 10,000 years before that, it was orbiting much farther from the Sun, safe
from the intense radiation.
This brought a relatively fresh comet from deep space into a region we could reach with
our spacecraft.
It's the perfect time capsule to tell us what the Solar System looked like eons ago.
The goal is to better understand how comets formed and what role they played in the early
Solar System.
Are they made from raw materials that clumped together during the formation of the Solar
System?
Were they processed through interactions with other objects in the Solar System?
Or are comets leftover chunks from shattered icy planets and other Kuiper Belt Objects?
Did they deliver water and organic materials to the early Earth to help life get going?
Now you know the history of cometary exploration and why the CAESAR mission is so important.
And in a second, I'm going to explain how the mission will work, but first I'd like
to thank:
Sherman Figura Steven Hill
Nicholas Verheyden Alexander Afanasyev
Rosemary Williams Gary Agnesini (Ag-na-si-ni)
And the rest of our 804 patrons for their generous support.
If you love what we're doing and want to get in on the action, head over to patreon.com/universetoday.
If all goes well, The CAESAR mission will launch in the summer of 2024 from Cape Canaveral.
It'll be equipped with an ion engine, allowing it to reach 67P in December of 2028.
The spacecraft will go into orbit around the comet, and then slowly lower its orbit over
several months, examining it in greater and greater detail.
It'll map out the surface, and search for any differences that have occured since Rosetta
made its maps, helping scientists understand how comets change over the course of a decade.
Mission planners will examine these surface maps and pick out candidate sites for CAESAR
to acquire its sample from.
Eventually, it'll be mapping out the surface down to a resolution of 0.6 cm per pixel.
Once the sites have been chosen, CAESAR will be ready to perform its touch-and-go operation
to sample material from the surface of 67P.
It'll have enough fuel on board for three attempts to get a sample.
The mission is inspired by NASA's OSIRIS-REx spacecraft, which is already on its way to
retrieve a sample from Asteroid Bennu.
So we'll already know if this technique is going to work.
The spacecraft will perform a deorbit burn, moving it closer to the surface of the comet.
Then it'll touch down for 5 seconds, suction up a bit of material, and then kick off into
space again.
It'll image the area at a resolution of 1 mm/pixel, giving scientists context for
where the sample came from.
Collecting the sample is going to be one of the toughest parts of the mission.
As we learned with Rosetta and Philae, trying to land on the surface of a comet is hard
enough.
Getting back out into space again is going to be even harder.
CAESAR is equipped with a special grabber called the Sample Acquisition System.
This is a suction cup-like device that can tilt to match the slope of the surface that
the lander touches down on.
When it senses the surface of the comet, it releases a set of spring-loaded ripper tines
that break up the crusty surface for easier collection.
Then it uses a pneumatic system to blast out high purity nitrogen gas around the sampling
cone, shaking up the comet material and directing it into the spacecraft's Sample Containment
System.
Up to 80 grams of cometary material will be captured for scientists at home to study.
But the actual cometary material is only half the story, the spacecraft will also pull out
any gases coming from the sample, and store that in a separate container.
This will give planetary scientists the best possible sample to study when it gets back
home.
It will then warm the samples to the exact temperature the comet experiences when it's
farthest from the Sun.
CAESAR will drift with Comet 67P for another 4 and a half years until it's in position
to make a burn back to Earth.
The sample will be transferred to a special landing capsule that will survive re-entry
through the Earth's atmosphere, delivering the pristine chunk of comet to waiting scientists.
And if all goes well, it'll return the sample to Earth in 2038, putting a piece of an actual
comet nucleus into the hands of scientists around the world.
By keeping it cold and pristine, researchers will be able to study it for clues for decades
to come.
Right now, NASA's OSIRIS-Rex mission is on its way to rendezvous with Asteroid Bennu
in 2018.
Then it will pick up a sample and return it back to Earth by 2023.
Planetary scientists will be able to study this sample in incredible detail, with the
best laboratories available to them here on Earth.
The CAESER mission will do the same, but provide a chunk of a comet to scientists to study.
Where did the Earth's water come from?
How early did organic materials form in the Solar System?
How did they come together to form planets?
By finally getting their hands on a chunk of a comet, scientists will have valuable
clues to these and many more questions about the Solar System.
Now it's Tim's turn.
Head on over to his channel and learn all about the Dragonfly mission to Titan.
And when you've made your decision, click the link in the shownotes to vote for your
favorite.
Whichever way you'd vote, let me know your thoughts in the comments.
Or just rage at the injustice of even having to choose in the first place.
Comet, Titan and why not, how about a mission to Venus?
Want more space news, I'm now writing a weekly email newsletter that highlights many
of the big stories that happened this week.
It's quick, easy to digest, with lots of amazing pictures and videos.
You can find out more and sign up by going to universetoday.com/newsletter
In our next episode, we return to the concept of artificial gravity.
There are some really interesting projects in the works that will attempt to create artificial
gravity for astronauts to live in.
And finally, here's a playlist, starting with a link over to Tim Dodd's half of the
collaboration.
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