New Horizons Pluto Presentation by Alan Stern at University of Alberta
On Monday Oct 5, 2015, Dr. Alan
Stern, the head of NASA’s New Horizons Pluto probe did a talk at the University
of Alberta. It was enormously well
attended and well received. Here are
some of my notes from the presentation, in point form.
The Speaker
·
Dr. Stern has a PhD in astrophysics and
planetary science. He has Masters
degrees in aerospace engineering and planetary atmospheres. Plus, of course, a B.Sc..
·
He is also involved in some private space
ventures, including Golden Spike, which is a private venture with the ambition
of returning to the moon.
·
Since boyhood, he always wanted to do space
science.
·
Among other things he has:
o Done
scientific work at the south pole.
o Flew
high performance jets for high altitude research.
o Been
involved in 26 space missions (including the shuttle).
o Been
involved in many planetary missions.
o Still
considers the Pluto mission to be the one that stands out the most.
Getting Funding for the Mission
·
The New Horizons Pluto fly-by came 50 years to
the day after the first Mariner fly-by of Mars.
·
Pluto, of course is the last planet to be
visited, while Mars was the first.
·
There has been a widespread desire for a NASA
mission to visit Pluto for decades, at least since the 1990’s. Funding has always been an issue, of course.
·
Even without good photos of Pluto (the best one
until New Horizons was from Hubble, and it showed only a small number of
pixels), there was general agreement that Pluto would be a very interesting
object.
·
As more was learned about the Kuiper Belt (Dr.
Stern used the pronunciation “Kwipper”), it was realized that Pluto was the
prime example of a whole new class of Kuiper Belt objects, rather than an
oddball “midget” planet, far off in isolation in the distant reaches of the
solar system.
·
Gerard Kuiper, in 1951, had theorized that there
should be a zone in the outer solar system from whence many comets originated.
·
In 1988 a team of Canadian researchers (Duncan,
Quinn, Tremaine) established conclusively that there must be a Trans-Neptunian
belt, where short-period comets originated.
·
Kuiper Belt objects then began to be discovered – 1 in 1992, 4 by
1993, 10 by 1194, over 1500 now.
·
In fact, it is now considered likely that there
are more Pluto sized planets than “regular” planets, as well as billions of
comets and hundreds of thousands of “planetoids”.
·
All of this gave impetus to a Pluto mission, now
that it was realized that it could teach us much about this new aspect of our
solar system.
·
Many programs were advanced, but New Horizons
was finally given the green light in 2003.
·
The spacecraft had to be designed an launched
within 50 months of getting the go-ahead, in order to catch the launch window
that would allow the Jupiter fly-by gravity assist. The timelines were tight, but they did it
(obviously).
·
They also did it within budget, or at least
pretty nearly so. Note that their budget
was only 20% of that allowed for the Voyager mission.
The Spacecraft
Photo from JPL New Horizons
·
The New Horizons spacecraft only weighs about
1000 pounds or 450 kilograms. That’s
about the size of a baby grand piano.
Voyager was much bigger.
·
Its plutonium powered generator put out about
250 watts at launch (that’s about the same as a solar panel on my garage). It’s now down to about 200 watts.
·
By the 2030’s, the power will probably have
decayed to a level that is too low to maintain communications with Earth.
·
Its instrumentation is small, but has a lot more
“firepower” than Voyager’s did, due to advances in computer science,
miniaturization, etc. That’s one reason
that so much can be done with only 200 or so watts of electricity.
·
There are seven science instruments in all,
including cameras, spectrometers, telescopes, dust counters, and plasma instruments.
·
As an example of technological change, a
spectrometer on Voyager had 1 pixel. A
similar instrument on New Horizons has 64,000 pixels.
The Launch
Photo from NASA media archives site
·
In January 2006, the spacecraft was launched
with an Atlas 5 rocket, the largest currently available (over 70 meters in
height). It has 5 rocket motors, each
about 25 meters long.
·
The rocket that propelled New Horizons out of
Earth orbit gave it a 14 gee kick (an acceleration of about 140 meters per
second per second).
·
It took 9 hours to cover the Earth-moon
distance, Apollo took several days.
·
This made it the fastest launch speed ever.
·
After that, it got a further speed-up, via a
gravitational assist from a Jupiter fly-by, in Feb 2007. The spacecraft steals a little bit of
Jupiter’s angular momentum, and gets accelerated in the process.
·
Some good science was done during the Jupiter
fly-by. This also allowed testing of
various spacecraft instruments, navigation and so forth.
·
Then, the spacecraft hibernated for 8 years. Mission personnel used this hiatus to do
extensive planning and scenario testing.
The Pluto Fly-by
:Photo from NASA mission pages
·
In January of this year, New Horizons was
awakened.
·
Some mid-course corrections were done, star
field photos were taken for navigation, etc.
·
By April, the images of Pluto and Charon began to
exceed those that Hubble had taken.
·
The fly-by, of course, occurred on July 14 (my
wife’s birthday).
·
The fly-by was fast, a matter of hours at
closest approach. So, a lot of science
was done in a short time, which required a lot of computer memory. The need to pivot the ship as it passed
Pluto-Charon made it temporarily out of contact, so that also necessitated
storing a lot of data.
·
Thus far, only about 10% of the data has been
transmitted to Earth.
·
New data comes in daily, via the deep space
tracking network. So, new things are
constantly being discovered. Multiple
experts pour over the data, from geophysicists, to particle scientists, to
astrophysicists, to … well, lots of different specialties.
·
Spoiler alert: Dr. Stern hinted that a big
discover was in the pipeline for later this week.
New Findings about Pluto and Charon
Photo from NASA mission pages
·
We now have good pictures of all of these:
o Pluto:
2400 km.
o Charon
(big moon): 1200 km.
o Nix
(little moon): 50km.
o Hydra
(little moon): 50km.
·
Nix and Hydra are cratered, very bright (ice?),
not round (too small).
·
Charon
o Has
a world spanning canyon.
o The
north pole is dark (tholins, a sort of nitrogen?).
o Some
craters have dark ejecta, some light.
o Charon
has a complex geology.
·
Pluto, “the other red planet”
o Note
that NASA has a 64 meg photo that you can download. This has surface detail down to 100 meters in
size.
o “The
Heart” (Tombaugh Reggio) is the biggest and brightest feature.
o Pluto
has an unexpectedly hazy, high atmosphere, which could be seen well in the
photos taken after the fly-by, back towards the sun.
o Mountains
are present, which was something of a surprise.
They show that the layer of nitrogen ice must be quite thin (nitrogen
ice won’t support much weight, so if the nitrogen layer was thick there would
be very subdued surface relief).
o At
minus 200 Celsius, water ice is hard as steel.
It could “build mountains”. The
nitrogen ice is just a frosting on the water ice.
o The
surface features dendritic patterns (like river valley systems on Earth). So, some fluid must have flowed in the past,
when the atmosphere was thicker.
o Some
ice fields feature “ovoids”, which would indicate convection cells in the ice
(something like bubbles in porridge, but happening on a glacial time scale). So, there must still be a heat source under
the surface, contrary to what theory had predicted.
o Sputnik
Planum has no craters, indicating that the surface has been “re-done” in the
recent (by geologic scales) past. Again,
this indicates that there must be a heat source.
o As
Dr. Stern put it, “Pluto’s engine is still running”.
o There
are other geological features (some huge) that were not expected. The same is true for Charon.
o Some
parts of Pluto and Charon are similarly coloured, a sort of red. Is the same process at work? Have they exchanged matter somehow?
o Pluto
may have a subsurface ocean. Data that
may help establish whether or not that is the case has not been downloaded yet
(but what about Thursday? Much
speculation about that announcement in the audience. Could it be the water announcement?).
o If
so, there is always a chance of life.
o The
heat source is perhaps the biggest surprise.
Nobody has come up with an explanation.
o The
mutual gravitation of Pluto and Charon shouldn’t be responsible, since they are
now tidally locked (though “a lot of smart people” have tried to make that
work).
o Later
note regarding the Thursday announcment: Pluto’s sky is blue and there is water
ice on the surface.
Media Response
·
A huge media response, as we know.
·
People love exploration, especially the idea of
“first contact” with an entirely new planet.
·
Perhaps this will create political pressure for
another mission to the Kuiper Belt (or beyond).
After the Fly-by
From JPL Where is New Horizons
·
New Horizons is on its way to a small (about 50
km) Kuiper Belt body.
·
It is expected that it will make a close
approach on Jan 1, 2019.
·
The spacecraft will eventually leave the solar
system.
·
It should be healthy until the 2030’s at least,
based on the decay time of the plutonium in its electrical generator. So, we should be getting feedback about the
outer solar system for decades.
·
There are many other fascinating Kuiper Belt
Objects which ought to be explored. No
doubt they would hold surprises for us.
All in all, it was a great talk. And I have a shirt just like the one he wore
under his jacket, so the man has style! :)
And here’s a link to the livestream of the presentation:
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And here's a link to a Dodecahedron books SF book, which involves lots of space travel, since my social media prof said you should always include a link to your book. Besides, all work and no play makes for a dull scientist:
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