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Cool Jobs: Exploring the solar system
This is one in a series on careers in science, technology, engineering and mathematics
made possible with generous support from Alcoa Foundation.
Even from a distance, scientists on NASA’s Dawn mission noticed something unusual
about Ceres. This dwarf planet is the largest object in the solar system’s vast asteroid
belt. It looked cold, barren and rocky. But that wasn’t the surprise. It was those strange
white spots.
As the spacecraft approached its destination, it began sending home more and better
pictures of Ceres (SEER-ees). But they didn’t solve the mystery.
“It’s been fun getting more detailed images of the white spots,” says Todd Barber. “They
get more and more intriguing, but we still don’t know what they are.”
Barber isn’t an astronomer or planetary scientist. As a propulsion engineer, he plays a
key role in helping scientists explore the asteroid belt: He steers the Dawn spacecraft.
What Dawn reveals about Ceres and Vesta, another large asteroid the spacecraft
visited, could help explain how our solar system formed.
People have been studying the sun and planets for thousands of years. Scientists,
though, still have many questions about Earth’s neighborhood. They search for clues
about what the solar system looked like in its earliest days, how planets were born and
how they ended up where they did.
And although it makes life possible on our planet and holds the entire solar system
together, the sun — and how it works — might be the biggest mystery of all.
Here are three people who are helping to explore and understand our solar system, from
its fiery center, to the distant asteroid belt and those frozen worlds beyond.
Steering a spacecraft
When Barber was asked to join Dawn, he was excited. An engineer at NASA’s Jet
Propulsion Laboratory in Pasadena, Calif., he had already worked on the Mars
Curiosity rover mission and the Cassini spacecraft. That last one was studying Saturn.
Now he would get to work on a spacecraft exploring two of the most intriguing objects
in the asteroid belt.
The main belt is a vast, donut-shaped cloud of space rocks. It floats between Mars and
Jupiter. Scientists believe this rubble was left over after true planets in the solar system
formed. Studying this belt of rubble should offer clues to the raw materials that created
the planets.
An artist’s illustration shows what the Dawn spacecraft might
have looked like as it arrived at Ceres.
Vesta is one of the largest asteroids in the belt. Dry and rocky, its resembles planets of
the inner solar system, such as Mars and Earth. Ceres looks more like the icy moons of
the outer solar system. NASA scientists hoped its two new asteroid targets would reveal
clues about two different space environments.
By the time Barber joined the team in 2014, Dawn had finished studying Vesta and was
on its way to Ceres. The plan was for the spacecraft to approach Ceres and drop into
orbit. It would fly lower and lower, taking pictures and mapping the surface of this dwarf
planet. It would continue making observations from that low orbit until the spacecraft
ran out of fuel.
But less than three weeks after Barber started working on Dawn, there was a problem.
One moment the spacecraft was thrusting toward Ceres. The next, it shut itself down
and went to sleep. The spacecraft had entered “safe” mode. It’s a way to protect itself
when something goes wrong.
Each day the spacecraft was shut down would delay its arrival at Ceres by nine days.
So Dawn was quickly falling behind in its race to catch up with Ceres’ orbit.
Barber and his new teammates worked around the clock to understand what went
wrong — and then how they might fix it. They were really concerned. Over time, they
had become attached to the little probe and wanted to make sure it was OK. “We think
of these things as if they’re humans,” Barber explains. “They have personalities and
quirks. When a family member is in trouble, you drop everything to go help them. And
that’s how you feel about these spacecraft.”
Finally, after four days, they found the problem. A tiny, radioactive particle had struck
the spacecraft. It had damaged an electronic part. To fix Dawn, they send the craft radio
commands on what to do. In short order this got it back on course and everyone was
relieved, Barber recalls. “JPL threw us a pizza party to celebrate.”
Ceres’ mysterious white spots are seen as it rotates, in these
images from the Dawn spacecraft.
NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Even though Dawn finished its trip across space and arrived at Ceres in March of this
year, Barber still needs to help steer it. The spacecraft must face Ceres when scientists
want to take pictures, then turn and point an antenna toward Earth to send those
pictures home. Barber controls and cares for the thrusters used to steer Dawn through
these maneuvers. “We point the spacecraft, we turn the spacecraft to and from the
asteroid, we control its orientation in space,” he says. Those thrusters fire small rockets
to push the spacecraft in different directions.
Barber checks things like fuel tank pressure and temperature. He monitors the opening
and closing of valves on the thrusters to make sure the propulsion system is working
properly. He also carefully reviews any planned movements. A mistake could cause the
spacecraft to crash.
“We have to be very careful with any commands we send to the spacecraft, to be sure
we’re not telling it to do something stupid,” he explains.
Barber loved science from an early age. “I was a mad chemist, burning holes in the
pavement and begging my parents to pipe [natural] gas into my room for a Bunsen
burner,” he recalls. (They wisely refused.) Later, he became fascinated with the Voyager
missions to Saturn and Jupiter and fell in love with planetary science. In college and
graduate school, he realized he could use his passion for chemistry and engineering to
help explore the solar system. So he studied aeronautics and rocket propulsion.
Today, his favorite part of working on Dawn is sharing in the mission’s discoveries.
“I’m right there with the scientists when the first pictures come back,” he says. “I totally
get jazzed by seeing stuff nobody’s ever seen before.”
Opening an asteroid “time capsule”
What’s inside an asteroid? Cristina Thomas hopes the answer might help explain how
the solar system formed some 5 billion years ago. This planetary astronomer studies
asteroid “families.” These are clusters of rocks and rubble floating in space that all
came from a big parent asteroid. That parent had een struck or smashed to pieces
during some large cratering event.
By looking at those smaller rocks, she hopes to see what had been inside their bigger
parent. Thomas is a research scientist at NASA’s Goddard Space Flight Center in
Greenbelt, Md. She works for the Planetary Science Institute and Universities Space
Research Association.
The families she hunts for are young, just a few hundreds of millions of years old.
“These young families are my time capsules from the early solar system,” she says.
“They have been opened fairly recently, and I hope that was enough to preserve what
was inside.”
Thomas studies sunlight bouncing off of these rocks to find out what they’re made of.
She knows that every element reflects light in a unique pattern of wavelengths, called a
spectrum. The pattern is like a fingerprint. She uses a tool called a spectrograph to
break apart the light reflecting off asteroids into its different wavelengths, much like a
prism separates white light into a rainbow. Then she compares the spectra from the
asteroids with those of elements found on Earth until she finds two that are the same.
“It’s a matching game,” she says.
When there’s an asteroid Thomas wants to study, she must first write a proposal. It’s a
document that explains what she’d like her project to tackle. It also asks for time on the
telescope she hopes to use. She often uses NASA’s Infrared Telescope Facility. The
telescope is in Hawaii, but Thomas can make her observations from the computer in her
home. When it’s her night to observe, she logs in to the facility’s computer with a
special password and calls the telescope operator. “Then I put on a pot of tea and
prepare to stay up all night,” she says.
Thomas often works with NASA’s Infrared Telescope Facility
(IRTF) in Hawaii to study asteroids in the main belt.
She tells the operator where to point and when to focus the telescope. Then Thomas
starts collecting data. “I’ll wake up the next morning or afternoon and download all the
data,” she says.
One mystery has been perplexing Thomas. Planetary scientists have gathered plenty of
evidence that suggests large asteroids should have melted at some time in their history.
Some elements in the rock are radioactive. Radioactive materials shed energy — heat
— as they decay (shed particles as their elements fission). That heat should have
caused melting. And if they melted, the rock should have differentiated. That means its
materials should have separated into layers, with the densest elements settling at their
cores.
Scientists know this happened. They just cannot find evidence of it in the asteroid
population. Where did that melted material go?
“What we see in the main belt now is very different from what we assumed would be
there,” Thomas says.
She hopes to find out whether the rocks within an asteroid family all look the same, or
whether smaller rocks are different from bigger ones. “Is there any evidence that they
melted in the past?” she wonders. “If we can figure that out, then we can start to
understand what happened in the early solar system.”
Eclipse chaser
The sun is Earth’s closest star. But because the sun’s extreme heat and radiation make
it difficult to investigate up close, there still are many things scientists don’t understand
about how it works. Why, for instance, is the sun’s corona — its outer atmosphere —
more than a million degrees hotter than its surface? And what’s the source of the solar
wind, a powerful stream of charged particles that flows out from the sun?
Next to the brilliant solar disk, and against a bright blue sky, the corona is almost
invisible. That’s one reason Shadia Habbal is willing to travel to some of the most
remote places in the world to observe a total eclipse of the sun. She is a solar physicist
at the University of Hawaii Institute for Astronomy in Honolulu.
Habbal and her team traveled to Svalbard, Norway, in March
2015 to observe a solar eclipse.
Dr. Miloslav Druckmüller
During a solar eclipse, the moon passes directly in front of the sun. Seen from Earth, it
appears to cover the solar disk. As the moon’s shadow passes over Earth, the sky turns
dark and stars can be seen, even though this occurs during daylight hours. For a few
minutes of “totality,” when the moon is directly in front of the sun, the corona will
become the brightest thing in the sky.
At that time, “you can see much further out in the corona,” Habbal says. Astronomers
can study the corona’s intricate structures, from its bright inner ring to the wispy plumes
of plasma that stretch far out into space.
Her goal is to discover what part of the sun the solar wind comes from. For years, many
scientists have argued that it comes from the sun’s poles, or from other features called
coronal holes, parts of the corona that are cooler and thinner. But Habbal has a different
theory. “For a long time, I felt it was from all over the solar surface. But I have yet to
prove it,” she says.
Close-up of the solar eclipse over Svalbard, Norway. Studying
it revealed the delicate structures of the sun’s corona.
When Habbal looks at an eclipse, she sees energy flowing out from the sun in every
direction. She hopes to find evidence that the solar wind behaves in a similar way.
During an eclipse, she takes pictures of the corona using special filters to see a unique
wavelength of light. That wavelength is due to the heating of iron atoms in the sun’s
corona.
Some atoms in the corona have been changed by radiation and heat. By using different
filters, she can compare the properties of iron atoms found in the corona with those
carried into interplanetary space on the solar wind. That should give her clues about
how the corona and the solar wind might be linked.
But studying eclipses isn’t easy. Total eclipses occur only about 75 times in every
century. They last no more than a few minutes. And the path of the moon’s shadow
often falls only on remote or extreme parts of Earth. Habbal must carefully plan how to
get her team of up to 20 scientists and technicians to these sites, along with their
delicate instruments and equipment.
Scientists traveling with Habbal set up their equipment before
the solar eclipse in Svalbard.
Dr. Miloslav Druckmüller
To see eclipses, she has already traveled to tiny atolls in Micronesia, to the middle of the
Libyan desert in northern Africa, to the African bush and to a frozen island in the Arctic
circle. She’s one of many eclipse chasers who is planning to educate the country about
safely viewing a solar eclipse that will pass across the United States in 2017.
And even though she spends years planning her expeditions, some end in heartbreak.
After traveling for days across rough terrain to set up their equipment, a sudden
rainstorm, a passing cloud or a foggy day might prevent her team from seeing an
eclipse. When that happens, they go home empty handed. Yet Habbal won’t go home
discouraged. Already she will be thinking about her next eclipse.
“You have to be an optimist,” she says. “The drive is so strong that you have to try
again. I’ve met a lot of eclipse chasers, and I haven’t met a single one that’s given up. It
becomes an addiction.”
Humans still know little about our closest neighbors in the universe — the sun, planets
and other bodies that make up our solar system. But we’re curious. So researchers like
the ones we’ve just met here have made it their job to investigate science and cosmic
history in our own backyard. ##
Power Words
(for more about Power Words, click here)
aeronautics The study of flight and development — or refinement — of craft to move
through air or space.
asteroid A rocky object in orbit around the sun. Most orbit in a region that falls
between the orbits of Mars and Jupiter. Astronomers refer to this region as the asteroid
belt.
astronomy The area of science that deals with celestial objects, space and the
physical universe. People who work in this field are called astronomers.
atoll
A ring-shaped island formed from a coral reef that surrounds a lagoon.
atom The basic unit of a chemical element. Atoms are made up of a dense nucleus
that contains positively charged protons and neutrally charged neutrons. The nucleus is
orbited by a cloud of negatively charged electrons.
bush (in landscape descriptions) The name for wild lands in certain countries,
especially parts of Africa and Australia.
Ceres
The largest known asteroid orbiting the sun. It sits 270 million kilometers
(nearly 168 million miles) from Earth in the asteroid belt between Mars and Jupiter. At
about 1,000 kilometers (600 miles) across, Ceres is so big that it is classified as a dwarf
planet. In 2014, astronomers found it spewing water from two places on its surface.
chemistry The field of science that deals with the composition, structure and
properties of substances and how they interact with one another. Chemists use this
knowledge to study unfamiliar substances, to reproduce large quantities of useful
substances or to design and create new and useful substances. (about compounds) The
term is used to refer to the recipe of a compound, the way it’s produced or some of its
properties.
corona The envelope of the sun (and other stars). The sun’s corona is normally visible
only during a total solar eclipse, when it is seen as an irregularly shaped, pearly glow
surrounding the darkened disk of the moon.
cosmos (adj. cosmic) A term that refers to the universe and everything in it.
crater A large, bowl-shaped cavity in the ground or on the surface of a planet or the
moon. They are typically caused by an explosion or the impact of a meteorite or other
celestial body. Such an impact is sometimes referred to as a cratering event.
decay (for radioactive materials) The process whereby a radioactive isotope — which
means a physically unstable form of some element — sheds energy and subatomic
particles. In time, this shedding will transform the unstable element into a slightly
different but stable element. For instance, uranium-238 (which is a radioactive, or
unstable, isotope) decays to radium-222 (also a radioactive isotope), which decays to
radon-222 (also radioactive), which decays to polonium-210 (also radioactive), which
decays to lead-206 — which is stable. No further decay occurs. The rates of decay from
one isotope to another can range from timeframes of less than a second to billions of
years.
density A measure of the consistency of an object, found by dividing the mass by the
volume.
dwarf planet
One of the solar system’s small celestial objects. Like a true planet, it
orbits the sun. However, dwarf planets are too small to qualify as true planets. Prime
examples of these objects: Pluto and Ceres.
eclipse The temporary masking of one celestial body (such as the sun or moon) by
another passing in front of it (from our vantage point on Earth). An eclipse can be full (or
total), where the more distant object totally disappears for a time, or partial, where some
part of it remains visible at all times to viewers on Earth.
element (in chemistry)Each of more than one hundred substances for which the
smallest unit of each is a single atom. Examples include hydrogen, oxygen, carbon,
lithium and uranium.
engineering The field of research that uses math and science to solve practical
problems. People who do this work are known as engineers.
fission The spontaneous splitting of a large unit into smaller self-sustaining parts. (in
physics) A process in which large atomic nuclei break apart to form two or more lighter
nuclei. The excess mass of the parent nuclei (compared to the resulting smaller ones) is
converted into energy.
graduate school Programs at a university that offer advanced degrees, such as a
Master’s or PhD degree. It’s called graduate school because it is started only after
someone has already graduated from college (usually with a four-year degree.
orbit The curved path of a celestial object or spacecraft around a star, planet or moon.
One complete circuit around a celestial body.
physicist A scientist who studies the nature and properties of matter and energy.
planetary science The science of other planets besides Earth.
plasma (in chemistry and physics) A gaseous state of matter in which electrons
separate from the atom. A plasma includes both positively and negatively charged
particles.
propulsion The act or process of driving something forward, using a force. For
instance, jet engines are one type of propulsion for keeping airplanes aloft.
radioactive An adjective that describes unstable elements, such as certain forms
(isotopes) of uranium and plutonium. Such elements are said to be unstable because
their nucleus sheds energy that is carried away by photons and/or and often one or
more subatomic particles. This emission of energy is by a process known as radioactive
decay.
rover A carlike vehicle, such as those designed by NASA to travel across the surface of
the moon or some planet without a human driver. Some rovers also can perform
computer-driven science experiments.
solar Having to do with the sun, including the light and energy it gives off.
solar eclipse An event in which the moon’s shadow covers the sun’s surface and
reveals its outer layer, the corona.
solar system The eight major planets and their moons in orbit around the sun, together
with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.
solar wind A flow of charged particles (including atomic nuclei) that have been ejected
from the surface of the star, such as our sun. It can permeate the solar system. This is
called a stellar wind, when from a star other than the sun.
spectrograph An instrument used to record light and separate it into its spectrum.
spectrum A range of related things that appear in some order. (in light and energy) The
range of electromagnetic radiation types; they span from gamma rays to X rays,
ultraviolet light, visible light, infrared energy, microwaves and radio waves.
telescope Usually a light-collecting instrument that makes distant objects appear
nearer through the use of lenses or a combination of curved mirrors and lenses. Some,
however, collect radio emissions (energy from a different portion of the electromagnetic
spectrum) through a network of antennas.
thruster An engine that pushes or drives with force by expelling a jet of fluid, gas or
stream of particles.
wavelength The distance between one peak and the next in a series of waves, or the
distance between one trough and the next. Visible light — which, like all
electromagnetic radiation, travels in waves — includes wavelengths between about 380
nanometers (violet) and about 740 nanometers (red). Radiation with wavelengths shorter
than visible light includes gamma rays, X-rays and ultraviolet light. Longer-wavelength
radiation includes infrared light, microwaves and radio waves.
valve
Something that can reduce or shut off the flow of some gas or liquid through a
pipe or other passageway. Some specialized valves may allow a liquid or gas to flow in
one direction only.
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