Archive for the ‘Planetary Science’ Category

Watching the Juno launch at NASA Goddard

Here are more than 200 of us at NASA/Goddard watching the Juno Mission blast off to Jupiter. A team of our scientists and engineers built an instrument Juno will use to study Jupiter’s mighty magnetic field.

To learn all the amazing stuff Juno will do when it reaches Jupiter in 5 years, see the excellent and detailed web feature by my friend Liz Zubritsky.

atlas rocket launching juno mission

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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There goes the neighborhood: What will the Webb Telescope reveal about our solar system?

Astronomer Heidi Hammel talks about how the Webb Telescope can be used to study our solar system.

Astronomer Heidi Hammel talks about how the Webb Telescope can be used to study our solar system.

The James Webb Space Telescope will look far back in cosmic time to study the origins of the universe.  But that doesn’t mean the observatory will turn a blind eye to the planets. Yesterday, at a conference at the Space Telescope Science Institute (STScI) in Baltimore,  noted planetary astronomer Heidi Hammel gave us a quick tour of the solar system from Webb’s (future) point of view.

UPDATE: A webcast video of Hammel’s talk is now available on the STScI website.

The conference, Frontier Science Opportunities with the James Webb Space Telescope (June 6-8), is all about what Webb can and will do once it makes it into space. It’ll be a while: As Matt Mountain, director of STSciI, mentioned in his opening remarks to the conference, Webb won’t see the cold of space, some 1 million miles from Earth, until at least 2017.

Hammel is known to be a great speaker, and she didn’t disappoint. First she took Mercury, Venus, and Earth out of the lineup. Her Powerpoint slides?

Mercury? No.

Venus? No.

Earth? No.

Webb’s orbit and the size and shape of its sunshield leave these planets in an “exclusion zone” hidden from the observatory’s view. (Its planned orbital perch is a point called L2, opposite from Earth with respect to the sun.) Ok, fine. What about Mars?

Yes. According to a March 9, 2010 White Paper about Webb and the solar system, the observatory could measure a number of important things in Mars’ atmosphere, like dust and carbon dioxide gas, that affect its climate.

Hammel speculated that Webb’s infrared eyes could help solve the mysterious nature of methane releases observed on Mars. Where does the methane come from? Webb might help us figure it out.

Jupiter? Saturn? Yes, yes. There is much Webb could learn about the atmospheres of these giant gas planets — which are, by the way, the best nearby examples we have of the scores of giant gaseous exoplanets being discovered in other solar systems.

Titan, Saturn’s largest moon? Yes. Webb could add a decade of observations of Titan’s surface and atmosphere to the work of the Cassini orbiter, and during a time in Titan’s seasonal cycle not yet explored in the infrared band, according to the White Paper.

Uranus and Neptune? An enthusiastic thumbs up from Hammel to the idea of studying these cool, distant bodies with the Webb’s infrared camera and spectrographs. She cited several scientific puzzles that Webb might help solve, including shifts in the wavelengths of light emitted by Uranus as the planet rotates and Neptune’s inexplicably warm polar region.

In general, Hammel said, “Neptune’s atmosphere is so dynamic, and little is known.” Anything Webb contributes will be helpful.

Last but not least, the region beyond Neptune, realm of Pluto and the other icy dwarf planets, is also fair game for Webb.  As the White Paper explains:

“Beyond Neptune, a class of cold, large bodies that include Pluto, Triton and Eris exhibits surface deposits of nitrogen, methane, and other molecules that are poorly observed from the ground, but for which JWST might provide spectral mapping at high sensitivity and spatial resolution difficult to match with the current generation of ground-based observatories.”

And comets, too. At least comets slow enough for Webb to track.

There has been much public hand wringing lately over growth in the Webb budget and slips in the launch date. But in the scientific community, two generations eagerly await the lofting of the giant Webb observatory into orbit. Many of them are up at STScI today sharing their plans.

“There’s a lot of great science that’s going to come out of this and I’m really looking forward to it,” Hammel said. “There is a wide range of interesting planetary phenomena observable by JWST, especially in the outer solar system.”

This NASA video goes into detail about planet studies — here and elsewhere in the universe — and the James Webb Space Telescope:

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.


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That Was the Week that Was, March 14-18, 2011. . . Best of Goddard People, Science, & Media and the blogpodcastotwittersphere

Tsunami Damage, Rikuzentakata, Japan

Tsunami Damage, Rikuzentakata, Japan

Japan Earthquake
After the March 12 earthquake and tsunami in Japan, it’s as if the world collectively gasped — and then what followed was almost a feeling of disbelief as the harsh facts begin to register. Entire seaside communities erased from existence. . . tens of thousands of lives feared lost. . . giant ocean swells flooding the coastline. . . cars and houses looking like toys bobbing in the water. And then there are the satellite images, which provide a critical wide-angle perspective.

NASA’s Earth-observing fleet has helped to reveal the full scope and power of the catastrophe. As Mark Imhoff, the Terra satellite project scientist at Goddard, said in a report by West Virginia Public Broadcasting:

“It’s been heart wrenching seeing some of these images because the first set images that we got in on the day after the earthquake on March 12, even though the resolution from of the satellite wasn’t very good, the data from the Miser instrument at Jet Propulsion’s Laboratory showed that there were a large area of coastline that really weren’t there anymore and so you could really get an impression that a lot of villages and agricultural areas had really been severely impacted by the ocean.”

NASA released a web feature on March 17, five days after the quake, showing tsunami after-effects documented by Landsat 7.

NASA Earth Observatory has compiled a gallery of earthquake-related images from various NASA spacecraft, including EO-1, Terra, Aqua, and astronaut photos from the International Space Station.

As usual, EO’s in-depth captions provide context and explanations for the various destructive effects of the earthquake on coastal Japan. An even larger selection of imagery is available in this NASA web feature about the disaster.


New LRO Data
On March 15, the Lunar Reconnaissance Orbiter mission released the final set of data from the mission’s exploration phase, along with the first measurements from its new life as a science satellite. The press release explains the details. The slideshow below takes a look back at some of the coolest imagery from the mission so far. All the images in the slideshow, and many more, are archived here on the NASA LRO website, which includes detailed captions.

Messenger Makes It
The third major story out of Goddard this week was the arrival in Mercury orbit of the Messenger spacecraft. After three spectacular fly-bys earlier (see slideshow below), Messenger is now in position to really dig into its science mission to reveal the nature and history of the first rock from the sun. An earlier post discusses some of the research being conducted on Mercury’s thin “exosphere” of atoms and ions wispily clinging within the planet’s gravity.

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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How to rip a moon apart

December 14, 2010 2 comments

artist concept of ice particles in saturn rings

We know that Saturn’s rings are ice particles orbiting the planet like a zillion tiny moons. But we’re not so sure how they got there. Surprised?

This week, a researcher at the Southwest Research Institute in Colorado, Robin Canup, published a new and intriguing hypothesis for what built Saturn’s rings as well as its inner moons. In a nutshell, Canup says multiple icy moons spiraled to their doom early in Saturn’s history, leaving behind the ice and rock that formed the rings and Saturn’s small inner moons.

Canup’s idea solves a few key problems for Saturn ring theorists. For more details, see the press release or a story by Discovery News writer Irene Klotz.

It’s hard to imagine a moon perhaps the size of Titan — around 5,150 kilometers (3,200 miles) across — getting torn apart. But it can happen, and the cause of it all is called tidal disruption.

Terry Hurford is a planetary scientist at Goddard who studies tidal disruption as it relates to Jupiter’s moon Europa and Saturn’s moon Enceladus. Gravitational tides alternately stretch and compress those bodies, causing cracking at the surface and interior heating.

On Europa, the degree of distortion is about 1 kilometer (0.6 miles) in extent. It’s not as clear about Enceladus, but Hurtford roughly estimates it could be around 500 meters.

But if a moon strays too close to its planet, the tides can stretch it to the breaking point. The threshold is known as the Roche limit. Once a satellite gets within that distance to its planet, the planet’s gravity is in charge and the moon literally can’t hold itself together.

“The body gets more and more distorted tidally,” Hurford explains. “The gravity from Saturn makes it more like a football shape, where you have this kind of a point of the football pointed toward Saturn. As you get closer, this distortion can grow really large. If you get close enough, you can distort the body so much that it no longer can hold onto its mass.”

And that’s exactly what Canup shows in her new computer simulation. Multiple moons stray inside Saturn’s Roche limit. Tidal flexing — the same thing that today occurs on Europa and Enceladus — melts the moon’s watery ices and separates them from rocky material. Eventually the ice gets stripped off entirely to form the rings and inner moons, and the rocky stuff plummets into Saturn.

Pretty dramatic! And it’s intriguing to think that Saturn might have once had several large moon, not just one. I think they deserve to at least be named, these lost satellites of Saturn.

How about: “Going, “Going,” and “Gone”?

Tidal Disruption of a Moon
[These illustrations appear in the Wikipedia entry for “Roche limit” and were created by Theresa Knott of English Wikipedia. The illustration shows a top view of a planet and its moon.]

illustration of tidal disruptionFar from the planet’s Roche limit (curved white line), the moon’s gravity molds it into a near-perfect sphere.

illustration of tidal disruptionAs the moon approaches the Roche limit, the planet’ s powerful gravity stretches and distorts the smaller satellite.

illustration of tidal disruptionAt the Roche limit, tidal forces overwhelm the moon’s own gravity, tearing the satellite into pieces.

illustration of tidal disruptionParticles inside the Roche limit orbit faster than those outside the limit. This causes the particles to spread out and form rings.
OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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The birth, life, and death of alien planets: Goddard exoplanet scientists give you an update on what we (think) we know

December 6, 2010 5 comments

exoplanet sun panorama

The official count of candidate planets around other stars recently hit a whopping 500. But when the first extrasolar planets — often called exoplanets — were discovered, many scientists weren’t sure if they should believe their own data. The first confirmed exoplanets were found around a stellar corpse called a pulsar, born of a supernova explosion of a star. And we also found lots of so-called hot Jupiters, huge steaming gasballs orbiting many times closer to their host stars than Mercury orbits the sun.

365 days of astronomy logoHow do exoplanets come to exist? How do they evolve over billions of years? And how do they die? If you’re curious and have 10 minutes, listen to my podcast, The Birth, Life, and Death of Alien Planets, on “365 Days of Astronomy.” (It’s a daily podcast produced by the International Year of Astronomy 2009.) You can also just download the (11 Mb) .mp3 file here and listen to it on your iPod or other media player. This blog post is adapted from the podcast transcript, if you prefer to read rather than listen to the 10-minute broadcast

The race is still on to discover more planets, and scores are promised thanks to missions like the Kepler space observatory. Meanwhile, down here on earth, exoplanets scientists are scratching their heads, mining their data, and tweaking their theoretical models to try and make sense of the diversity of alien worlds we have already found.

Here at NASA’s Goddard Space Flight Center, where I work as a science writer, we’ve got a whole group of scientists obsessed with exoplanets. They took me on a whirlwind tour of the birth, life, and death of planetary systems. It all starts with a collapsing cloud of gas that forms an infant stars surrounded by a spinning disk of gas and dust — the stuff of which planets are made. A protoplanetary disk.

JENNIFER WISEMAN: Young protostars are buried in a large envelope of dense gas, kind of flattened like a fluffy pancake, but it can extend out to thousands of astronomical units, the distance from the Sun to the Earth.”

DANIEL PENDICK: That’s Jennifer Wiseman. She studies star birth and is the new senior project scientist for the Hubble Space Telescope. She’s also the chief of Goddard’s ExoPlanets and Stellar Astrophysics Laboratory, which is home to many of the exoplanet researchers here at Goddard.

WISEMAN: You have this puffy but dense sort of pancake of gas, swirling around, and in the interior part of this, material is being gravitationally sucked into a tighter accretion disk that’s right around this young forming star.

PENDICK: OK, so far so good. We’ve got an accretion disk, which is where planets come from. What happens next? I asked Hannah Jang-Condell, a post-doctoral researcher at Goddard and the University of Maryland. She’s also a member of the Goddard Circumstellar Disks Group, about a dozen scientists here active in exoplanet research.

JANG-CONDELL: So basically you’ve got a star. It’s not burning hydrogen yet. You’ve got this disk of gas and dust surrounding it. And planets are starting to form in this disk.

PENDICK: Hold on — did she say dust? As in those fluffy dust bunnies that inhabit the underside of my couch? Not exactly. When astronomers say dust, they mean tiny bits of solid stuff, like minerals and ices, floating around in space. The dust grains are on the scale of a micron—a millionth of a meter—in diameter.

JANG-CONDELL: It’s assumed that as you build these things up from the micron size to the centimeter size, that things stay fluffy. So sort of loosely bound aggregates. So they are a lot like dust bunnies at that stage.

PENDICK: So much for interstellar dust bunnies. Now, back to the planet building stage of our story.

JANG-CONDELL: So there’s two main scenarios for the way planets form. There is the core accretion scenario. So you start out with dust particles and they collide and coagulate and become larger and larger bodies. When it gets about 10 to 20 times Earth’s mass it’s able to accrete gas, and then the gas will stay on it. From that point it can accrete gas and become a gas giant planet like Jupiter.

The alternative scenario is called gravitational instability. In that case, you have a massive disk, and it’s cool enough and dense enough for it to start self-gravitating. So in other words, the disk will fragment, it will start to form a clump, the clump will become self gravitating, and eventually it will collapse to form a giant planet.

PENDICK: This all takes place in the space of a few million years — a cosmic blink of an eye. Gas giants have to form before all the gas in the system has either accreted onto the star or is blown away by the star’s radiation.

Once the gas goes away, the infant planetary system evolves into something called a debris disk. As Goddard exoplanet researcher Aki Roberge explains, the planet-building process continues in debris disks, creating larger and larger bodies called planetesimals. In today’s solar system, planetesimals are known as asteroids and comets.

AKI ROBERGE: They start colliding and sticking. Roughly speaking, it’s just hit-stick-hit-stick, get bigger and bigger and bigger.

PENDICK: Sometimes the collisions are not so sticky. The planetesimals smash together and generate lots of smaller debris particles. In fact, huge dusty disks were discovered around other stars for the first time in the 1980s. Astronomers dubbed them ‘debris disks.’

ROBERGE: Over the years, there’s been lots of pieces of evidence collected that these debris disks, they really are young planetary systems. So they are like young, dense versions of our own Kuiper and asteroid belts, and our own solar system probably went through a phase very much like it, a debris phase, when it was young.

So any giant planets that would form in the system have already formed because there is no gas left to form any giant planets. And some planetary embryos, maybe Mars sized bodies, are there already. So what’s happening is the late stage of terrestrial planet formation. So you are building up from Mars to real Earths.

PENDICK: Terrestrial planets can have violent births, as embryonic planets up to the size of Mars slam into others and build up larger planets. Also at this time, water rich comets may stream in and collide with the young terrestrial planets. This provides the raw material for oceans and atmospheres.

Theory tells us these events must be happening in the dusty disks astronomers study. But we don’t see any of this directly.

ROBERGE: All you can really see, ironically enough, is the very smallest portion. So what you see is the dust, tiny, tiny little dust [grains.] This is the dust that’s produced when two asteroids crash together and break up, or the dust that’s in a comet’s coma that’s being expelled as they evaporate. So actually we see the indirect signs. We can see the tiniest material but we know it has to be coming from bigger things.

PENDICK: At some point, things do settle down a bit. But even in a mature planetary system, the action is far from over. Planets continue to migrate in their orbits, or even be ejected from the system in hair-raising close encounters. And if a planet orbits close enough to its star — even closer than Mercury orbits the sun — it could spiral inward and be consumed. In short, entire planets disappear from planetary systems. Goddard exoplanet researcher Brian Jackson explains.

BRIAN JACKSON: Once you get that close, tides raised on the host star and tides raised on the planet can affect the orbit of the planet. Because the rotation of the star is so much slower than the rate at which the planet is going around, the bulge tends to point a little bit behind the planet. And you can think about the gravitational interaction with that bulge always pointing behind the planet a little bit kind of yanks back on the planet and that can reduce the orbital distance between the host star and the planet.

Eventually its orbit will shrink enough that it will be destroyed. That can happen within a few billion years. So a lot of these close-in planets that we see aren’t going to last more than a few billion years.

PENDICK: And even planets farther out from the star can experience dramatic changes because of tidal forces.

JACKSON: If the planet’s orbit is non-circular, then what happens is the size of the tidal bulge when the planet is closest to its host star is bigger than when the planet is farther away. The shape of the planet will change as it goes around in its orbit. That change, that periodic flexing of the planet, dissipates energy inside of the planet. It can drive volcanism, which can cause outgassing and provide an atmosphere for the planet. And we see this sort of volcanism powered by tides in our own solar system, for example, Jupiter’s moon Io undergoes the same sort of tidal heating…and that drives the volcanoes that erupt on the surface of Io.

PENDICK: In fact, tidal flexing could hypothetically turn the surface of a rocky planet into a lava sea fuel massive supervolcanoes. Or it could cause just enough heating to maintain a warm and stable climate, as earthly plate tectonics does on our world.

We used to think that solar systems eventually settle down and become middle-aged and sedentary, with stable and predictable behavior. But this does not appear to be the case.

JACKSON: Among planetary systems, the rule seems to be that interactions can be very violent and dynamic and the orbits can evolve pretty dramatically over time.

PENDICK: Planetary systems can even come back from the dead after the most violent event nature has to offer — the supernova explosion of a star. Goddard post-doctoral scientist John Debes has studied these born-again planetary systems. In fact, the first planets ever discovered around other stars were found orbiting a pulsar — the superdense rotating remnant of a star that went supernova.

JOHN DEBES: What people think happened is that after the initial supernova explosion some of the material fell back into a disk, and that allowed these smaller planets to form. And the only reason we found them is because pulsars are amazingly precise clocks, and you could measure the timing of the pulses of the pulsar, and see that that would change due to the orbital wobble of these planets.

What’s great about that system, even though it’s the only one that’s been found, is it really shows the sort of basic process for forming a planet must be pretty easy to do, because if you can do it in the fallback disk of a supernova, you can do it just about anywhere if you have the right amount of material and the right conditions.

PENDICK: Hot Jupiters spiraling to their fiery doom… planets par boiled in molten lava… worlds born from the ashes of dying stars. It sure isn’t your grandfather’s solar system science anymore, with well-behaved old planets in their stately settled orbits. As telescopes give us even sharper views of alien worlds, it’s hard to predict what strange world await discovery.

Astronomer Carolyn Crow, also the center of the solar system.
OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.

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Gogblogcast #4: Sample Analysis at Mars Open House: getting to know you, getting to know all about you. . .

November 24, 2010 Leave a comment

Download a transcript of this video.

The Goddard community began the process of saying good-bye to the Sample Analysis at Mars (SAM) instrument with an open house event. SAM will soon be off to NASA’s Jet Propulsion Laboratory in Pasadena, California, to be installed on the Mars Science Laboratory rover “Curiosity.” If all goes according to plan, the Mini Cooper-sized robot will blast off to Mars in 2011 and land in August 2012.

SAM contains a suite of three instruments that will search for compounds of the element carbon, including methane, that are associated with life and explore ways in which they are generated and destroyed on Mars. The instruments, developed by an international team, all came together at Goddard and underwent rigorous testing. Goddard people will play a key role in operating and supporting SAM when it reaches the Red Planet and starts roving.

So long, SAM! Safe journey.

Pan Conrad, SAM Deputy Principal Investigator, gives an overview of the Curiosity rover and the SAM instrument suite.

Pan Conrad, SAM Deputy Principal Investigator, gives an overview of the Curiosity rover.

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.