This is Pluto.
An icy world located 7.5 billion kilometers from Earth.
And recently, the best images we had were nothing more than a few pixels captured by
the mighty Hubble Space Telescope.
But now, thanks to NASA’s New Horizons, we know it’s an amazing world, with mountains
made of ice, glaciers of nitrogen, and even a tenuous atmosphere.
Although the flyby happened 3 years ago, this isn’t the end of the journey for New Horizons.
It’s got one more encounter in just a few months.
Another meeting that will fill in even more gaps in our knowledge about the Kuiper Belt.
An encounter with Ultima Thule, the most distant object humans have ever reached.
I did a whole video on New Horizons, so I don’t want to get too deep into it again.
But here’s the quick version.
Planetary scientists have wanted to send a mission to Pluto for decades.
As far back as 1989, Alan Stern and another dozen planetary scientists created a group
called the Pluto Underground.
Their goal was to figure out the kind of mission that could reach out to Pluto, a world that
wasn’t reached during the Voyager missions.
After several missions were proposed over the decades, the New Horizons spacecraft was
finally accepted and designed.
It was launched towards Pluto in 2006.
It took New Horizons almost 10 years to reach Pluto, getting a gravitational assist from
Jupiter along the way.
On July 14, 2015, the spacecraft made its closest approach to Pluto, seeing the world
and its moon Charon up close for the first time.
The spacecraft was equipped with seven scientific instruments, designed to photograph the surface
of these worlds in several wavelengths, measure their atmospheres, features, temperatures,
and chemical makeup.
The pictures sent back to Earth from New Horizons were dramatic, a vast improvement over the
blurry pixels provided by the Hubble Space Telescope.
As always, a close encounter like this offered up more mysteries than it solved, which will
keep planetary astronomers busy for decades.
But New Horizons isn’t done.
It recently found a fascinating wall of hydrogen around the Solar System.
And in another few months, it’s going to make its next flyby: Ultima Thule.
Let’s talk about what else has been discovered by New Horizons.
What can we expect to see when it reaches Ultima Thule on New Year’s Day, 2019.
And what plans are in the works for new missions that will go back to Pluto and Charon.
Not just to flyby, but to orbit, and maybe even land on the surface.
It’s time to go back to Pluto.
Although New Horizons made its Pluto flyby over three years ago, it took the better part
of 16 months to send all its data back.
With a transmission speed of only 1-2 Kbps, it took that long to transmit all the data
it captured in just a few days.
Then New Horizons went to sleep again, until July, 2018 when it was woken up by NASA, and
prepared for its encounter with Ultima Thule, also known as 2014 MU69.
Very little is known about Ultima Thule.
It was discovered by the Hubble Space Telescope just two years ago, and measures about 30
kilometers across.
Just for comparison, that’s about 5 times bigger than Comet 67/P, visited by ESA’s
Rosetta Mission, and about 60 times bigger than asteroid Bennu, the target of NASA’s
OSIRIS-REx mission.
Spacecraft operators just published new images of Ultima Thule captured by New Horizons.
It’s just a tiny little speck in the spacecraft’s camera, but this is an impressive accomplishment
considering the fact that it’s still 160 million kilometers away - greater than the
distance from the Earth to the Sun.
New Horizons will make its closest approach to Ultima Thule on January 1st, 2019, passing
within just 3,500 kilometers of the Kuiper Belt Object.
This is three times closer than the spacecraft got to Pluto and Charon.
It should be capable of seeing features on the surface as small as 30 meters across.
Is it a single object?
A rubble pile?
A contact binary like 67P?
We just don’t know anything else about the object yet.
I can’t wait to see those first pictures.
What happens after that is unknown.
New Horizons still has some fuel in the tank and if other Kuiper Belt Objects are discovered
along its flight path, it could be redirected again for another encounter.
Another recent piece of news from New Horizons was the discovery of a vast wall of hydrogen
surrounding the Solar System.
The discovery was made with the Alice instrument on board New Horizons, which picked up a faint
ultraviolet glow beyond the Solar System’s heliopause.
This is a bubble that surrounds the Sun, pushed out by the solar wind which collides with
the background winds from the rest of the stars in the Milky Way.
On the far side of the heliopause, New Horizons detected the faint signal of neutral hydrogen
atoms piling up outside this bubble; a vast wall of hydrogen first seen by the Voyager
spacecraft.
New Horizons will continue to observe this region every few months, to help astronomers
piece together the environment at the farthest reaches of the Solar System.
We’ve seen our first tantalizing images of Pluto, but of course, planetary scientists
want to learn more.
They want to go back with a new mission, that could even land on the surface of Pluto.
And we’ll talk about these plans in a moment, but first I’d like to thank:
Michael Stephen Bradley Joseph Hart
Douglas Smith Laura Sanborn
Ed Williams Barnard Rabenold
Jacob Miller
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As incredible as the New Horizons Pluto encounter was, the reality was that the spacecraft was
only able to image about 40% of Pluto and Charon during its flyby at resolutions of
10 km per pixel or less.
Furthermore, the spacecraft wasn’t able to image any of Pluto’s other tiny moons
in high resolution.
It’s amazing to think that the dramatic features we see on Pluto and Charon are less
than half the story.
Of course, the close up flyby generated more questions than it answered for Pluto researchers.
Why does the world have such active glacier processes?
Does it have any kind of cryovolcanism?
What kind of geologic process could have generated such enormous mountain ranges?
Is there a liquid ocean underneath the ice?
Do the other sides of Pluto and Charon look anything like the sides we’ve already seen?
In order to get some answers, researchers would like to send an orbiter or even a lander
back to Pluto.
As I mentioned in a previous video about upcoming space telescopes, researchers across space
science are setting their science goals as part of the 2023 Decadal Survey.
In a recent paper entitled, “A White Paper on Pluto Follow On Missions: Background, Rationale
and New Missions Recommendations”, a team of planetary scientists put forward why a
return mission to Pluto should be a priority for NASA, and what different kinds of missions
would be possible.
In terms of missions, they proposed three options: another flyby, an orbiter and a lander.
The flyby would be a low cost mission that would be timed so that it sees as much of
the terrain as possible that New Horizons missed.
It could have a new suite of instruments designed to study the Pluto environment, and gather
additional data.
Once the flyby of Pluto was complete, it could go on to study other Kuiper Belt Objects.
Sounds pretty familiar.
An even more exciting idea would be to send an orbiter.
This would be a larger, flagship mission that would take a slower trajectory to Pluto but
be able to go into orbit to stay.
Over the course of several years, the spacecraft would be able to intensively study all the
worlds in the Pluto system.
It would be able to help answer questions uncovered by ongoing research.
And the most exciting option would be to attach a lander, similar to how the European Huygens
probe was attached to NASA’s Cassini at Saturn.
This lander would detach from the orbiter, land on the surface of Pluto, and study it
from close up.
A mission to Pluto would be very similar to NASA’s Dawn mission, using an electric ion
engine to generate the kind of enormous velocities to get out to Pluto relatively quickly.
But unlike Dawn, which is closer to the Sun at the Asteroid Belt, a Pluto Orbiter would
use a decaying chunk of plutonium as a battery to run its thruster and science instruments.
According to Alan Stern, the Principal Investigator of New Horizons, an orbiter mission on a powerful
rocket would probably need about 7-11 years to cross the distance from Earth to Pluto,
depending on the launch vehicle; ideally some time between 2026 and 2028.
And then it could spend years and years studying the Pluto system.
Once there, a mission would be able to image the rest of Pluto and Charon at very high
resolution, and even take time to take pictures of the rest of its moons.
It would be equipped with instruments designed to investigate the features discovered at
Pluto, like ground penetrating radar, mass spectrometers, thermal mappers and altimeters.
By staying at Pluto for a long time, a mission could watch how the icy world changes as it
drifts farther and farther from the Sun in its orbit.
New Horizons observed the atmospheric haze around Pluto, but a return mission would be
able to measure the chemicals in the atmosphere, determine how big the particles are.
Is there weather?
And the science of Charon would be as interesting as Pluto itself.
There are signs of ancient plate tectonics on the surface of Charon.
When did that shut down?
What caused these red stains on the surface of the world?
A longer term mission could study the rest of Pluto’s moons, since there’ll be many
opportunities for close flybys.
We only got a quick introduction to Pluto and Charon, and as you can see, there are
so many additional questions that only a long term mission could help answer.
Of course, we could say that about almost every corner of the Solar System.
It’s a huge place, and we’ve only explored a fraction of it.
It’s really exciting to think that we’re only a few months away from New Horizons’
close encounter with Ultima Thule.
The chance to see another world in the Kuiper Belt.
And it’s even more exciting to know that there are plans in the works to return to
Pluto.
I know I want to see more.
What do you think?
Would you advocate for a mission to Pluto?
Let me know your thoughts in the comments.
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