EDUCATION: PLUTO PEN PALS
Favorite Questions
SOME OF OUR FAVORITE QUESTIONS:
Where do shooting stars come from?
Could New Horizons crash into Jupiter?
Could life exist on Pluto?
How do spacecraft avoid collisions with asteroids?
Could a person jump into orbit around Pluto?
Tell us a little about the SDC
Why don’t they change Uranus’ name?
Why does Earth have only one moon?
What classes should I take to become an engineer?
Why do moon rocks stay on the moon?
QUESTION TO: Kris Larsen
QUESTION: Where do shooting stars come from?
ANSWER:
Shooting stars are, unsurprisingly, not stars at all. They are small pieces of dust, rock, or
ice that are orbiting the Sun, like the Earth, and which run into the
Earth like a cosmic auto accident. Their proper name are meteors. If they
survive their trip through the atmosphere and strike the ground, then they
are called meteorites.
Take a quick poll among yourselves. How big do you thing the
meteors you see in the night sky are? As big as a watermelon? A baseball?
A grape? A pea? Or the size of the head of a pin? The vast majority of
meteors you see are the size of a pea or even smaller. Of course, there
are some that are much, much larger. Every now and then people find
meteorites the size of their fist that have either hit recently or which
fell thousands of years ago. And every so often, really big meteorites hit
the Earth. A few thousand years ago, a meteorite the size of a small car
landed in Arizona and made a crater over a mile across
http://neo.jpl.nasa.gov/images/meteorcrater.html.
And scientists believe that 65 million years ago a meteorite
about 10 kilometers across struck the gulf coast of Mexico, digging a huge
crater and throwing so much dust and ash into the atmosphere that the
Sun's light was blocked. The end effect of this meteorite was the
extinction of the dinosaurs (which was fortunate for us mammals as we then
came to dominance, which seems to have turned out pretty well for us).
I mentioned that every so often people find meteorites. This is
true, but not very common. Most of the time, when someone finds a rock
they think might be a meteorite, it turns out they just found an
interesting rock that was formed here on Earth. Scientists who study
meteorites are always interested in finding new meteorites that can tell
them something about the Solar System. In order to find new meteorites,
they have to go to places on Earth where they don't expect to find any
rocks. The best place for this is Antarctica. Since Antarctica is covered
predominantly in snow and ice, any rocks that you find sitting on the
ground probably fell there from space. Every year a team of scientists
goes to Antarctica and spends several weeks camping on the ice and returns
home with several hundred new meteorites to study.
Finally, you might wonder why scientists would spend their lives
studying meteorites in the first place. There are a couple good reasons to
study meteorites. First, the majority of meteorites formed at the same
time as the solar system (about 4.5 billion years ago) and have been
orbiting the Sun ever since. This means they are small glances into what
the Solar System was like when it formed. By studying the elements and
minerals in the meteorites we can learn where our planet came from.
Secondly, some meteorites haven't actually been floating around in space
for billions of years .Some of them actually come from the Moon or even
Mars. If a really big meteor hits either the Moon or Mars, it will throw
lots of rocks into space and some of these may eventually make their way
to Earth. So by carefully studying the meteorites we find, we may actually
be able to study what the other planets are made of without having to
spend millions of dollars to go collect rocks and bring them home. Of
course, since we're reliant on luck as to what rocks are thrown into space
and make it to the Earth, it doesn't give us a very detailed look at the
other planets, so we'll still have to go their ourselves if we want to
really understand them.
Ok. Once again, I've written about a lot more than simply where
shooting stars come from, but I hope you don't mind. I also have a
question for you this week. I haven't gotten to spend much time in the
East and haven't yet visited West Virginia. Do you live in an area that
has a lot of mining?
Sincerely, Kris
QUESTION FROM: Eileen Poling’s Class, Tucker Valley Elementary Middle School, Hambleton WV
QUESTION TO: Jenny Young
QUESTION: Is there a possibility that New Horizons could get lost in Jupiter instead of getting a gravity boost from it?
ANSWER:
If the spacecraft were to come too close to Jupiter, it could potentially be pulled into the planet’s orbit or crash on it, but we take precautionary measures to make sure that this doesn’t happen. We need to get close enough to Jupiter to get a gravity assist and change our trajectory, but not too close so that we don’t get trapped. It helps that we always know the trajectory and the position of the satellite when it is out in space. One instrument that assists with this is called a “star tracker” and it has a database of star charts that it uses to compare to the stars that it sees outside. This way we can tell what orientation the satellite is in. We can also change the trajectory by sending signals from Earth if we find out that we are getting too close to Jupiter. New Horizons is not the first satellite to use Jupiter on the way to somewhere else. I found an animation that shows the gravity assist that the satellite Cassini used from Jupiter to get to Saturn:
http://www.esa.int/esaSC/SEMXLE0P4HD_index_0.html
QUESTION FROM: Barry Fried and Honora Dash’s class, John Dewey High School, Brooklyn, NY
QUESTION TO: Frank Eparvier
QUESTION: Could life exist on Pluto?
ANSWER:
It’s possible, but highly improbable. Life requires energy to thrive. On Earth most life gets it energy, either directly or indirectly, from the Sun. Because Pluto is so far away, it gets, on average, 1/1560th the amount of sunlight that Earth gets. That means it is very cold there, with temperatures ranging from -390° to -345°F! That’s so cold that oxygen and nitrogen, the main components of air on Earth, will turn to ice! Life also relies on chemical reactions, but reactions slow down to almost a dead stop when it gets as cold as it is on Pluto. It’s doubtful that life could have formed there, but even on Earth life is very adaptable, so maybe if life were brought there from somewhere else, it might find a way to survive, but it would be more difficult than any conditions encountered anywhere on Earth.
QUESTION FROM: Barry Fried and Honora Dash’s class, John Dewey High School, Brooklyn, NY
QUESTION TO: Frank Eparvier
QUESTION: How is math used to help scientists figure out the path the space craft will take so that it does not get hit by objects in space, like asteroids and comets?
ANSWER:
Mathematics is used in every step of the process. The forces of gravity and the motions and interactions of objects can all be described with mathematical equations. We have equations that tell us where all the planets will be at any time in the future. We know the mass of our spacecraft and can write the equations of the forces that the rocket motors at launch, and the planets and other bodies in space will exert on our spacecraft, so we can make equations to calculate where our spacecraft will be at any point along its journey, and we can plan a path that doesn’t collide with anything else that we know about. We can also use math to fibure out how to make our spacecraft go where we want it to, if we discover a new object that it needs to avoid. We also track out spacecraft. If it doesn’t go where we predicted it should have, we can make adjustments to get it back on course and we can use math to figure out what we got wrong with our predictions. For instance, the individual masses of Pluto and Charon are not known very well. As New Horizons approaches it we can tell from the way the spacecraft reacts to each body’s gravity how far off we were in our estimate of their masses.
QUESTION FROM: Eileen Poling’s Class, Tucker Valley Elementary Middle School, Hambleton WV
QUESTION TO: Jenny Young
QUESTION: Does a human have enough energy to jump into orbit around Pluto?
ANSWER:
The amount of energy a human can produce depends on their velocity and mass. The equation for kinetic energy is KE = (1/2)mV2. The velocity that it takes to get away from Earth without falling back to the surface is called the escape velocity. For Earth, it’s about 11 km/s (that’s the same as 24,606 mph, which is why we need something really fast like a rocket to get to space). Since Pluto has less gravity and a smaller diameter, the escape velocity is much less at 1.3 km/s (2,908 mph). So it would be a lot easier to send a rocket into orbit around Pluto then around Earth, but a human still wouldn’t be able to jump up with enough velocity to make it into orbit around Pluto.
QUESTION FROM: Michele Benson’s Class, Buckhannon Upshur Middle School, Buckhannon WV
QUESTION TO: Vaughn Hoxie
Mr. Vaughn Hoxie,
Hello my name is Brittany and my partners are James, Dusten and Cassie. We are excited to be your pluto pen pals!
The first question my class was wondering is the SDS an actual instument that will collect space dust and send it back to earth? Your letter mentioned a launch in January. How exciting! Will this be a probe or is this another shuttle scheduled to go up? What is the destination of the launch vehicle?
A couple of other students Jessica and Elizabeth had a question about age. You mentioned very specifically you were the oldest team member. Do you think age and maturity make you see a mission differently than a young staff? What kind of opportunities will the SDS provide?
Can you tell us a little more about the MESSENGER spacecraft? When it was launched? Can the MASCS actually try and bring sample back or does it monitor and send pictures ect. How long will it take to get to Mercury?
We had someone from NASA guest speak at our school. Mrs. Rudo Kashiri, she talked about some the future goals. It is neat to know we have a pen pal involved with the furture of NASA.
Thank you for sharing your time with us. We truly appreciate you.
Sincerely,
Michele Benson and The Buckhannnon Upshur Buccaneers
REPLY:
Hello Brittany, James, Dusten and Cassie also Jessica and Elizabeth and the rest of the Buccaneers.
I’m happy to hear from you all!
Let me give a little background on the Student Dust Counter and the mission it’s flying on. In the process I can answer some of your questions. The Student Dust Counter (SDC) is one of several science instruments mounted on the New Horizons deep space probe. New Horizons is scheduled to be launched on January 11 on a one way mission to, and beyond the outermost planet Pluto! Because New Horizons is on a one way trip, it’s not really possible to return samples back to Earth. Instead SDC will measure and record whatever dust it encounters on its trip and report its measurements back to Earth.
As its name suggests, the Student Dust Counter was designed and built by students, specifically college students here at the University of Colorado (Ok, yeah some people have suggested that the name might mean we measure dust from college students, but we don’t). In addition, SDCs operations throughout the mission will be directed and monitored by future students here. SDC is the first interplanetary instrument ever designed or built by students.
Your question about whether my age lets me see the mission differently is a good one. Yes, age probably made me look at things differently, but the team was so diverse I’m sure we all saw it from very different points of view. Our team consisted of about 16 students, half undergraduates and half graduate students. Their fields of study included mechanical, electrical, aerospace and software engineering, physics and planetary sciences and we had a communications student who documented much of the project. About a third of the team was women, including one with a young son. We had four foreign students two from Hungary and one each from Thailand and India. Some team members were around 18 years old, some were in their mid to late twenties and there was me. What being older definitely gave me was more experience working on complex projects to draw from, and maybe a little more patience for some of the practices and regulations required to fly on a NASA deep space mission.
On to your questions about the MESSENGER mission to Mercury. It was launched from Kennedy Space Center in August 2004. Its flight path to Mercury is long and complex. It will loop around the Sun many times swinging by the Earth once (this last August), Venus twice and Mercury three times before settling into an orbit around Mercury in 2009. During its Earth flyby this last August, one of the cameras onboard took a spectacular sequence of images that have been assembled into a movie you can see at the move page (http://messenger.jhuapl.edu/the_mission/flyby_movies.html) of the MESSENGER website (http://messenger.jhuapl.edu).
Once at Mercury the spacecraft will orbit for about 12 months while the instruments photograph the entire surface, map the minerals and geological formations, measure the make-up of the very thin atmosphere and study the planets magnetic field and how it interacts with the strong solar winds. The instrument I worked on, MASCS (Mercury Atmosphere and Surface Composition Spectrometer), will take spectral data the surface and atmosphere in the ultraviolet, visible and near infra-red wavelengths to determine what they are made of. All of this data will be sent back by radio, again no samples will be returned.
I think that’s all for this email. Take care,
Your pen pal, Vaughn
QUESTION TO: Kris Larsen
QUESTION: Dear Kris, We are having a discussion as we write you back about the name of Uranus. Why did NASA change the pronunciation? Why not change the name completely?
Sincerely, Mrs. Tipton's class
ANSWER:
Ah, the seventh planet and the butt of many a joke given its name.
I'm not completely sure about NASA changing the pronunciation, I haven't
heard of any official discussion about the name. There are basically two
camps when it comes to the pronunciation. American English would have us
pronounce the name as 'yure-eh-nus', with the emphasis on the second
syllable. Traditional British pronunciation is similar, but giving way to
'yoor-a-nus', stressing the first syllable. Which is correct is a matter
of taste. Obviously, the first pronunciation sounds similar to certain
other words that may produce laughter, but it isn't incorrect.
Now, about changing the name completely. Uranus was the first
planet discovered using telescopes by William Herschel on March 13, 1781.
For the next seventy years it was called 'Herschel' by some and 'Georgium
Sidus' by others. The latter name translates as .The Georgian Planet.,
named such by Herschel because his boss was the King of England, King
George III (the same one that America won its independence from a few
years earlier). Around 1850, the planet was renamed Uranus to continue the
pattern of naming planets after gods from classical mythology. Uranus,
the God, was the Greek deity of the Heavens, one of the Titan's that
later gave rise to Zeus, Hera, and the whole pantheon. If you remember
the discussion we had a few weeks ago about whether Pluto is or isn't a
planet, and the controversy that has engendered in the astronomy
community, you might guess at how difficult it would be to change the
name of a large planet. As changing the name isn't really an option, we
all must simply stifle our laughter when saying it's name.
QUESTION TO: Kris Larsen
QUESTION: Why does Earth only have one moon when other planets have so many?
ANSWER:
Good question. Especially with Cassini exploring the many moons of Saturn
and the recent possible discovery of two new moons around Pluto.
How many moons a planet has depends greatly on how moons form. As a planet
grew during the early stages of the solar system, moons can form in the
same way. Each begin as a clump of rock, ice, and dust which slowly
collects additional material. As it gets bigger, it's gravitational field
increases and it can gather more material. Eventually, the planet is big
enough that it sweeps clear a region around the Sun. While this is
happening, smaller clumps that orbit the planet can also be accreting
material. When most of the rock and dust surrounding the Sun has been
collected we're left with planets and moons. This is what happened,
mostly, with the majority of the moons of Saturn and Jupiter. Moons that
form in this manner tend to orbit nearly in the equatorial plane of the
planet and in the direction the planet is rotating. This is a result of
the planets and moons following a fundamental law of physics, the
conservation of angular momentum.
A second way for moons to end up in orbit around a planet is for them to
be 'captured' by the planet. If a large asteroid or body comes too close
to a planet, it can be caught in the planet's gravitational field and end
up orbiting the planet. The two moons of Mars, Phobos and Diemos, both
were captured in this way. The large outer planets, Jupiter, Saturn,
Uranus, and Neptune, also have captured moons. These moons don't have to
orbit in the equatorial plane or in the same direction as the planet since
they did not form along with the planet. They can, but they don't have to.
Finally, a moon can form from a planet's material but after the planet
itself has already accreted. We think this is how the Earth's moon formed.
Early in the Earth's history, we think it was struck by a very large
asteroid. The impact almost destroyed Earth, throwing a huge amount of
material into orbit. This material then began to accrete while in orbit
and eventually formed the Moon.
So, that's the different ways moons can form around planets, but why does
Earth have one, Jupiter has sixty three, and Venus none? Because of the
first way moons form, larger planets will tend to have more moons because
of their larger gravitational field clears a larger area around the Sun of
material. That's why the big outer planets all have a large number of
moons. Because the capture of asteroids and other small bodies is somewhat
of a random process, any planet can have them as moons. However, the
closer a planet is to a source of asteroids (like the asteroid belt
between Mars and Jupiter), the more likely one of those asteroids will be
captured. Thus, Mars has captured its two moons and many of the smallest
moons of Jupiter are also captured bodies.
Finally, having a moon created by large impact, like the Earth's,
is a completely random process. When the Earth was hit it could have been
completely destroyed and it's material captured by Mars and Venus. Or the
Earth could have re-accreted all the material and not formed the Moon.
It's a cosmic coincidence that we have a moon to watch at night.
Have a great week.
Kris
QUESTION FROM: Eileen Poling’s class, Tucker Valley Elementary Middle School, Hambleton WV
QUESTION TO: David Summers
Hello David,
The students are excited to have an engineer who grew up in WV as a pen pal. I'm thrilled because they need to hear more about WV students who have gone on to succeed in important professions!
We're reading Coalwood Way, by Homer Hickam, Jr. They wondered if you'd ever read any of his books or if you've been to Coalwood. He also graduated from Virginia Tech, I think.
They also want to know what courses you took in high school to prepare as an electrical engineer. Of course, they want to know how hard the college classes are, too!
Take care! Talk to you soon.
Eileen
ANSWER:
I have read “Rocket Boys” by Homer Hickam, but I have not read “Coalwood Way”. I liked “Rocket Boys” a lot. I also built and launched model rockets when I was a kid.
Math classes are very important if you want to become an engineer or scientist. Taking advanced math classes like Calculus in high school will help a lot with your college math and engineering courses. I always had at least one math class every year of college and sometimes had two or three different math classes at the same time.
Now that I am working, I use a calculator or a computer to do most of my math for me, but I know that I would never get the correct answers if I hadn’t learned to do the math by hand first. A computer is only as smart as the person using it, so you still need to know the theory behind the calculations. The computer just makes things a lot faster.
I would also suggest that everyone should learn a computer programming language as early as possible. Computer programming is important in any technical field, not just computer science or engineering. I know of people who work in many different fields that write their own computer programs to make their jobs easier.
My favorite classes in college were the robotics related classes such as:
*Microprocessor Systems : We learned to program a small microprocessor called the Motorola 68HC11 and then built projects based on the microprocessor. I designed a build a small robot out of the remote controlled car. The robot could see and follow a second remote controlled car that was driven by a human. It made for a fun game to try to outrun the robot before it caught the human driven car.
*Mechatronics : This class was a joint class between the Mechanical Engineer department and the Electrical Engineering department. We learned how to design and build mechanical systems that are controlled by computers. Robots fall into this category, but so do a lot of other types of machines. For example all modern cars have engines that are controlled by computers.
Talk to you soon,
David Summers
QUESTION TO: Kris Larsen
QUESTION: If there is no gravity in space then how do the moon rocks stay on the
surface of the moon?
ANSWER:
To begin with, let's talk a little about what gravity is and
isn't. Gravity is an inherent property of everything that has mass. The
more mass an object has, the stronger it's gravitational field. Each of
you, sitting in your desks, have a gravitational field that is acting upon
everything around you. But, since I doubt any of you weigh as much as the
Earth, the strength of your gravitational field is very, very small and
you can't tell that you're pulling your classmates towards you (and they
are pulling you towards them). Instead, all we 'feel' is the Earth's
gravity that keeps our feet on the ground.
Another property of gravity is that it's strength decreases with
distance. It's very similar to what you've seen when you play with
magnets. When a piece of iron gets close to a strong magnet, it will be
attracted to the magnet and can even move across a smooth desk. But as you
move the iron further away from the magnet, the strength of the attraction
gets smaller and smaller. It is the same with gravity. The further you
get from an object, the weaker it's gravitational field.
As for rocks on the surface of the moon, they are held on the
surface for the same reason rocks sit on the ground here on Earth. The
moon is smaller than the Earth, but it is still a very large object and
has it's own gravitational field. The moon's gravity is about 1/6th that
of Earth's (because the moon is so much smaller than the Earth). So, if
you weigh 75 pounds on the Earth, you'd only weigh 15 pounds on the moon.
But that's still enough that you'd be able to walk around the moon and
stay 'stuck' to it's surface.
Those rocks on the surface of the moon stay on the moon because
the moon attracts them with it's gravity. And, because the Earth has an
even stronger gravitational field, the moon stays in orbit around the
Earth, much like satellites stay in orbit around the Earth. And both the
Earth and Moon (as well as all the other planets) stay in orbit around the
Sun because of it's enormous gravitational field.
Have a great week,
Kris
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