What did NASA’s New Horizons discover around Pluto?

In 2015, there was a huge excitement in the
space community. That is because up until then, the best image
we had of the Pluto system was this. Hubble also squinted its lens at Pluto, but
it is so small and distant, the best it couldsee was a few blobs of colour variation. But in 2015, this all changed. That is because after a nine year journey,
the New Horizons space probe flew by the dwarfplanet, giving us a detail and fidelity of
Pluto and its moons like we had never seenbefore. So the question is, what did the New Horizons
probe see and discover during its flyby ofthe Pluto system?I’m Alex McColgan, and you’re watching
Astrum. Stick with me in this video and I will show
you all the highlights from the New Horizonsmission to Pluto. Pluto was the last of the traditional 9 planets
to be explored. This was due to its distance from us, but
also because – can you believe this – itwasn’t considered a very interesting celestial
object. Thankfully, the New Horizon’s team pushed
hard for this mission to be approved, andin 2006, New Horizons launched as part of
NASA’s New Frontier’s program, for mediumbudget space missions. The goal of the mission was to get to Pluto
as soon as possible, and as such, New Horizonswas the fastest launch ever, it being a light
spacecraft on the most powerful rocket ofthe time – the Atlas V. It whizzed past
the moon in only 9 hours. The Apollo missions took 10 times as long. On its way to Pluto, it used Jupiter as a
gravity assist which shaved 3 years off thearrival time. It also used Jupiter as a trial run for its
systems, taking some remarkable videos andimages of the planet and its moons. After this successful trial, New Horizons
went into hibernation mode to prevent wearand tear of its instruments. Leading up to its approach in 2015, the team
turned the systems back online, and everyday the spacecraft sent back images of the
Pluto system. This was an incredibly exciting time for enthusiasts
following the story. We began to get hints of what Pluto could
possibly look like, and saw how differentPluto was from its biggest moon, Charon. Every day, the resolution got higher and higher,
and more details could be made out. Yes, there were other scientific goals for
the mission, but the most interesting thingto me was what it looked like. Soon there could be seen what looked to be
a heart shape on the dwarf planet!On the 14th July, the New Horizons probe made
its closest approach, at only 12,500 km fromthe surface of Pluto. However, mission controllers didn’t get
a look straight away. Firstly, the probe was too busy taking a lot
of photos during the flyby to send any backimmediately. Once data transfer commenced, they had to
deal with the slow uplink speed of only 1kbit/sec. Further to that, there was a 4. 5 hour latency
between the spacecraft and the Earth. But what it saw and sent back was spectacular:
mountain ranges, ice plains, glaciers andan atmosphere. It also had a good look at some of Pluto’s
moons. Let’s go into detail about what it actually
discovered during this flyby. One of the first things observed about the
Pluto is its unusual relationship with itsmoons. For a start, Pluto’s biggest moon, Charon,
orbits very closely to Pluto, and is alsovery big in comparison. This means that the barycentre of the two
objects, or in other words, their centre ofmass, is outside of the primary object. They actually both orbit around a point in
space. Not only that, but both objects are tidally
locked to each other. This means if you stand on one, the other
won’t move from that point in the sky. This is very unusual because while some moons
are tidally locked to their parent planet,the planet is not also tidally locked to the
moon. Charon is very different visually from Pluto
being much darker. This implies they are not from the same origin. The rest of Pluto’s moons are very small,
only being a few kms across. Their orbits are exceptionally circular and
are all coplanar with Pluto’s orbit. The geology of Pluto is very interesting. The biggest visible feature on Pluto is this
giant heart shape, which wowed the world whenit first came into view. It has since been named Sputnik Planitia. It is the size of Texas, and it has a strong
colour contrast to the surrounding area. This is because it is a giant ice plain. In fact, during the flyby, it was confirmed
that 98% of Pluto’s surface is comprisedof nitrogen ice. On average, the temperature on the surface
of Pluto is -229c, which means water ice wouldbe rigid and brittle. On the other hand, nitrogen ices at this temperature
act like water ice on Earth, meaning it canflow as glaciers. This can especially be seen around the edge
of the heart, glaciers flowing into the gapsaround the craters and mountain ranges. The ice plains themselves have giant polygon
shapes across the entire area. There also are no craters, which means it
must be a relatively new feature, or a featurethat is being continually renewed. It is perhaps only 10 million years old. The polygonal cells show ridges on them which
are likely caused by sublimation, the processof an ice turning directly into a gas. Although it’s not known for certain, Sputnik
Planitia could have formed from an impact,and ices filled the crater in from a potential
subsurface liquid ocean. This filled in basin actually causes a positive
gravitational anomaly. A gravitational anomaly is where the gravity
at one point is different from elsewhere onthe object. The ice plain is directly facing away from
Charon, which would align it up with the objects’tidal axis. Due to the short distance between Pluto and
Charon, tidal effects are very strong on bothobjects. This could be the reason why Pluto is tidally
locked to Charon and the two objects can’tlook away from each other. Surrounding the ice plains are vast mountain
ranges made of water ice, which, when viewedfrom the side on, look spectacular. Water ice is the only type of ice detected
on Pluto that would be strong enough to supportheights of several kilometres at this temperature. Among the mountains found on Pluto, there
might also be some which are cryovolcanoes,one of the most likely candidates being Wright
Mons. It is 4 kms tall, one of the highest peaks
on Pluto, and a big depression is found inthe centre. Cryovolcanoes could be a contributing factor
for Pluto’s young surface. Another obvious feature of Pluto is the dark
material that seems to be sprinkled on thesurface in some areas. The biggest such area is called Cthulhu Macula. It is weirdly reminiscent of a whale in shape,
as can be seen in this image. The dark colour is thought to be a deposit
of tholins, a kind of tar made up of hydrocarbonsthat have interacted with sunlight. Similar deposits can be seen on one of Saturn’s
moons, Iapetus, so the process has been seenelsewhere in the solar system. The region on Pluto is much more heavily cratered
than the heart, which implies the surfacethere is much older. Mountain ranges can be seen in the middle
of Cthulhu Macula, topped with what is thoughtto be methane ices. Methane apparently condenses as frost at higher
altitudes on Pluto. The last surface feature I will mention here
is this region called Tartarus Dorsa. It is an extensive, highly distinctive set
of 500-meter-high mountains that resemblessnakeskin or tree bark. They are thought to be Penitentes. If that is true, Pluto is the only place in
our solar system other than Earth where theyhave been observed. Even on Earth they are very rare, but some
can be found in the Atacama desert and otherdry, high altitude regions. The ones on Pluto are much taller and cover
a much vaster area than on Earth. We can only imagine what they look like close
up. For me, the most impressive discovery that
New Horizons was able to confirm was thatPluto has an atmosphere. And not only that, but the images are incredible. Due to Pluto’s small size and weak gravity,
the atmosphere appears to extend high abovethe surface of Pluto. Earth’s atmosphere, while being much more
massive and dense compared to Pluto, hugsthe planets comparatively tightly as the gravity
is a lot stronger. The atmospheric pressure on Pluto is exceptionally
low, however, roughly 10 microbars, or 100,000– 1,000,000 times weaker than the surface
pressure on Earth. It is theorised that the pressure could increase
to as much as 18 to 280 millibars, three timesthe surface pressure on Mars and a quarter
of the surface pressure on Earth, if the temperaturewas to rise and the surface ices would sublime
into gases, the process which we’ve seenin the ice plains. The last time Pluto was thought to have this
atmospheric density was 900,000 years ago. At this pressure and temperature, the conditions
could even be right for liquid nitrogen toform on Pluto’s surface. Some evidence of this might be found here,
in what appears to be a frozen over lake. At any rate, within just one year, Pluto’s
atmospheric density can vary by a factor offour due to seasonal variations. That is a massive contrast compared to other
solar system objects with atmospheres, whichgenerally stay pretty consistent. The atmosphere consists of the same ices found
condensed on the surface, namely nitrogen,methane, and carbon monoxide. The other fascinating discovery New Horizons
made about the atmosphere is that it has upto 20 haze layers. Haze layers themselves were not unexpected,
but the amount of them was. They can clearly be seen in some of these
images, acting like layers of a thin kindof fog. Sunlight can be seen streaming through one
such layer in this photo, the shadows fromthe mountains clearly seen in contrast to
the sunlight shining through the haze. The layers do not appear to be level across
the planet. Here you can see this haze layer high above
the surface, but on this side of the imageit touches the surface. On a side note, to me these are the most breath-taking
photos of Pluto, and I purposefully savedthem until last. You can truly appreciate depth and the scale
of the mountain ranges; Pluto almost seemslike a toy replica due to the extreme topographical
relief, but these mountains appear so highbecause Pluto is so small, and its gravity
is not strong enough to pull them down. This gives for a varied and impressive landscape
and a fitting end to the video. Did you enjoy what you saw today?Watching videos is great, and if you want
to broaden and retain that knowledge, thebest way to do so is to actively grapple with
puzzles and problem solving. That’s why for these last two videos, Astrum
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so do check them out. The data New Horizons sent back to Earth will
continue to be pored over for years to come. New Horizons has a new mission in its sights
though, a flyby of a small Kuiper Belt Objectknown as 2014 MU69, due to arrive on the 1st
January 2019. If you want to find out about this mission
and also see the dedicated Pluto video I willmake in the future, please subscribe so you
don’t miss out. Also check out the other videos I’ve made
about a variety of astronomy topics. Thanks for all your support, and I’ll see
you next time.