Posted on by Fraser Cain

How Dense is the Asteroid Belt?

How Dense is the Asteroid Belt?

We’ve seen way too many science fiction episodes that show asteroid belts as dense fields of tumbling boulders. How dense is the asteroid belt, and how to spacecraft survive getting through them?

For the purposes of revenue, lazy storytelling, and whatever it is Zak Snyder tells himself to get out of bed in the morning, when it comes to asteroids, Science fiction and video games creators have done something of disservice to your perception of reality.

Take a fond trip down sci-fi memory lane, and think about the time someone, possibly you, has had to dogfight or navigate through yet another frakkin’ asteroid belt. Huge space rocks tumbling dangerously in space! Action! Adventure! Only the skilled pilot, with her trusty astromecha-doplis ship can maneuver through the dense cluster of space boulders, dodging this way and that, avoiding certain collision.

And then she shoots her pew pew laser breaking up larger asteroids up into smaller ones, possibly obliterating them entirely depending on the cg budget. Inevitably, there’s bobbing and weaving. Pursuit craft will clip their wings on asteroids, spinning off into nearby tango. Some will fly straight into a space boulder.

Finally you’ll thread the needle on a pair of asteroids and the last ship of the whatever they’re called clicky clacky mantis Zorak bug people will try and catch you, but he/it won’t be quite so lucky. Poetically getting squashed like… a… bug. Sackhoff for the win, pilot victorious.

Okay, you probably knew the laser part is totally fake. I mean, everybody knows you can’t hear sounds in space. Outside of Starbuck being awesome, is that at all realistic? And if so, how does NASA maneuver unmanned spacecraft through that boulder-strewn grand canyon death trap to reach the outer planets?

The asteroid belt is a vast region between the orbits of Mars and Jupiter. Our collection of space rocks starts around 300 million kilometers from the Sun and ends around 500 million kilometers. The first asteroid, the dwarf planet Ceres which measures 950 km across, was discovered in 1801, with a “That’s funny.”. Soon after astronomers turned up many more small objects orbiting in this region at the “Oooh neat!” stage.

Artist’s concept of Dawn in its survey orbit at dwarf planet Ceres. Credit: NASA/JPL-Caltech
Artist’s concept of Dawn in its survey orbit at dwarf planet Ceres. Credit: NASA/JPL-Caltech

They realized it was a vast belt of material orbiting the Sun, with I suspect a “We’re all gonna die.”. To date, almost half a million asteroids have been discovered, most of which are in the main belt.

As mentioned in a another video, gathering up all the material in the asteroid belt and gluing it together makes a mass around 4% of the Moon. So, in case one of your friends gets excited and suggests it was a failed planet, you can bust out that stat and publicly shame them for being so 1996, Goodwill Hunting style. You like asteroids? How about them asteroids?

There’s a few hundred larger than 100 km across, and tens of millions of rocks a hundred meters across. Any one of these could ruin a good day, or bring a bad day to a welcome firey close for either a depressed wayfaring spacecraft or a little bluegreen speck of a planet. Which sounds dangerous all the way around.

Fortunately, our asteroid belt is a vast region of space. Let’s wind up the perspective-o-meter. If you divide the total number of objects in the field by the volume of space that asteroid belt takes up, each space rock is separated by hundreds of thousands of kilometers. Think of it as gravity’s remarkably spacious zen rock garden.

Ceres compared to asteroids visited to date, including Vesta, Dawn's mapping target in 2011. Image by NASA/ESA. Compiled by Paul Schenck.
Ceres compared to asteroids visited to date, including Vesta, Dawn’s mapping target in 2011. Image by NASA/ESA. Compiled by Paul Schenck.

As a result, when NASA engineers plot a spacecraft’s route through the asteroid belt, they don’t expect to make a close encounter with any asteroids – in fact, they’ll change its flight path to intercept asteroids en route. Because hey look, asteroid!

Even though Ceres was discovered in 1801, it’s never been observed up close, until now. NASA’s Dawn spacecraft already visited Asteroid Vesta, and by the time you’re watching this video, it will have captured close-up images of the surface of Ceres.

Once again, science fiction creatives sold us out to drama over hard science. If you’re passing through an asteroid belt, you won’t need to dodge and weave to avoid the space rocks. In fact, you probably wouldn’t even know you were passing through a belt at all. You’d have to go way the heck over there to even get a nearby look at one of the bloody things. So we’re safe, our speck is safe, and all the little spacecraft are safe…. for now.

Which dramatic version of “asteroids” are you most fond of? Tell us in the comments below.

Posted on by Bob King

Scientists in Orbit Over Dawn’s Arrival at Ceres

The slim crescent of Ceres smiles back as the dwarf planet awaits the arrival of an emissary from Earth. This image was taken by NASA’s Dawn spacecraft on March 1, 2015, just a few days before the mission achieved orbit around the dwarf planet. Because of its angle of approach (see video above) Dawn saw Ceres from its backside, which from its perspective, was mostly in darkness. Credit: NASA/JPL


Dawn’s approach and trajectory as it begins its orbital “dance” with Ceres. As you watch, note the timeline at upper right.

Dawn made it! After a 14-month tour of the asteroid Vesta and 2 1/2 years en route to Ceres, the spacecraft felt the gentle tug of Ceres gravity and slipped into orbit around the dwarf planet at 6:39 a.m. (CST) Friday morning.

“We feel exhilarated,” said lead researcher Chris Russell at the University of California, Los Angeles, after Dawn radioed back the good news. 

 

Not only is this humankind’s first probe to orbit a dwarf planet, Dawn is the only spacecraft to fly missions to two different planetary bodies. Dawn’s initial orbit places it 38,000 miles (61,000 km) from Ceres with a view of the opposite side of Ceres from the Sun. That’s why we’ll be seeing photos of the dwarf planet as a crescent for the time being. If you watch the video, you’ll notice that Dawn won’t see Ceres’ fully sunlit hemisphere until early-mid April.

Dawn’s spiral descent from survey orbit to the high altitude mapping orbit. The trajectory progresses from blue to red over the course of the six weeks. The red dashed segments are where the spacecraft is not thrusting with its ion propulsion system (as explained in April). Credit: NASA/JPL - See more at: http://dawnblog.jpl.nasa.gov/2014/06/30/dawn-journal-june-30-2/#sthash.CZ2WGsDQ.dpuf
Dawn’s spiral descent from survey orbit to the high altitude mapping orbit. The trajectory progresses from blue to red over the course of the six weeks. The red dashed segments are where the spacecraft is not thrusting with its ion propulsion system. Credit: NASA/JPL

The spacecraft will spend the next month gradually spiraling down to Ceres to reach its “survey orbit” of 2,730 miles in April. From there it will train its science camera and visible and infrared mapping spectrometer  to gather pictures and data. The leisurely pace of the orbit will allow Dawn to spend more than 37 hours examining Ceres’ dayside per revolution. NASA will continue to lower the spacecraft throughout the year until it reaches its minimum altitude of 235 miles.

As Dawn maneuvers into orbit, its trajectory takes it to the opposite side of Ceres from the sun, providing these crescent views. These additional pictures were taken on March 1 at a distance of 30,000 miles (49,000 km). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
As Dawn maneuvers into orbit, its trajectory takes it to the opposite side of Ceres from the sun, providing these crescent views. These additional pictures were taken on March 1 at a distance of 30,000 miles (49,000 km). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

“Since its discovery in 1801, Ceres was known as a planet, then an asteroid and later a dwarf planet,” said Marc Rayman, Dawn chief engineer and mission director at JPL. “Now, after a journey of 3.1 billion miles (4.9 billion kilometers) and 7.5 years, Dawn calls Ceres, home.”

More about Dawn’s incredible accomplishment can be found in the excellent Dawn Journal, written by Dawn chief engineer and mission director Marc Rayman.

Posted on by Bob King

What Asteroid 2004 BL86 and Hawaii Have in Common

Toes of a pahoehoe flow advance across a road in Kalapana on the east rift zone of Kilauea Volcano, Hawaii and the binary asteroid 2004 BL86. Credit: U.S. Geological Survey (left) and NASA/JPL-Caltech

At first glance, you wouldn’t think Hawaii has any connection at all with asteroid 2004 BL86, the one that missed Earth by 750,000 miles (1.2 million km) just 3 days ago. One’s a tropical paradise with nightly pig roasts, beaches and shave ice; the other an uninhabitable ball of bare rock untouched by floral print swimsuits.

But Planetary Science Institute researchers Vishnu Reddy and Driss Takir would beg to differ.

Using NASA’s Infrared Telescope Facility on Mauna Kea, Hawaii they discovered that the speedy “space mountain” has a composition similar to the very island from which they made their observations – basalt.

“Our observations show that this asteroid has a spectrum similar to V-type asteroids,” said Reddy. “V-type asteroids are basalt, similar in composition to lava flows we see in Hawaii.

Minerals on the surface of an object like the moon or an asteroid absorb particular wavelengths of light to create a series of "blank spaces" or absorption lines that are unique to a particular element or compound. Credit: NASA
Minerals on the surface of an object like the moon or an asteroid absorb wavelengths of light to create a series of “blank spaces” or absorption lines that are unique to a particular element or compound. Credit: NASA

The researchers used a spectrograph to study infrared sunlight reflected from 2004 BL86 during the flyby. A spectrograph splits light into its component colors like the deli guy slicing up a nice salami. Among the colors are occasional empty spaces or what astronomers call absorption lines, where minerals such as olivine, pyroxene and plagioclase on the asteroid’s surface have removed or absorbed particular slices of sunlight.

You're looking straight down on the 310-mile-wide Rheasilvea crater / impact basin on the asteroid Vesta. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
You’re looking straight down into the 310-mile-wide (500 km) Rheasilvea crater / impact basin on the asteroid Vesta. It’s though that many of the Vesta-like asteroids, including 2004 BL86, originated from the impact. It Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

These are the same materials that not only compose earthly basalts – all that dark volcanic rock that underlies Hawaii’s reefs and resorts – but also Vesta, considered the source of V-type asteroids. It’s thought that the impact that hollowed out the vast Rheasilvia crater at Vesta’s south pole blasted chunks of mama asteroid into space to create a family of smaller siblings called vestoids.

 

This animation, created from individual radar images, clearly show the rough outline of 2004 BL86 and its newly-discovered moon. Credit: NASA/JPL-Caltech
This animation, created from individual radar images, shows the binary asteroid 2004 BL86 on January 26th.  The moon’s orbital period is about 13.8 hours. Credit: NASA/JPL-Caltech

So it would appear that 2004 BL86 could be a long-lost daughter born through impact and released into space to later be perturbed by Jupiter into an orbit that periodically brings it near Earth. Close enough to watch in wonder as it inches across the field of view of our telescopes like it did earlier this week.

The little moonlet may or may not be related to Vesta, but its presence makes 2004 BL86 a binary asteroid, where each object revolves about their common center of gravity. While the asteroid is unlikely to become future vacation destination, there will always be Hawaii to satisfy our longings for basalt.

Posted on by Jason Major

Here’s Dawn’s Best View of Ceres Yet

Animation of Ceres made from Dawn images acquired on Jan. 13, 2015 (Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI)

Just sit back and watch the world turn… or should I say, watch the dwarf planet turn in this fascinating animation from Dawn as the spacecraft continues on its ion-powered approach to Ceres!

The images were captured by Dawn’s framing camera over the course on an hour on Jan. 13 at a distance of 238,000 miles (383,000 km) from Ceres. At 590 miles (950 km) wide Ceres is the largest object in the main asteroid belt.

“Already, the [latest] images hint at first surface structures such as craters,” said Andreas Nathues, lead investigator for the framing camera team at the Max Planck Institute for Solar System Research in Gottingen, Germany. “We have identified all of the features seen by Hubble on the side of Ceres we have observed, and there are also suggestions of remarkable structures awaiting us as we move even closer.”

Although these latest 27-pixel images from Dawn aren’t quite yet better than Hubble’s images from Jan. 2004, very soon they will be.

Comparison of HST and Dawn FC images of Ceres taken nearly 11 years apart
Comparison of HST and Dawn FC images of Ceres taken nearly 11 years apart

“The team is very excited to examine the surface of Ceres in never-before-seen detail,” said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. “We look forward to the surprises this mysterious world may bring.”

Launched Sept. 27, 2007, Dawn previously spent over 13 months in orbit around the asteroid/protoplanet Vesta from 2011–12 and is now on final approach to Ceres. On March 6 Dawn will arrive at Ceres, becoming the first spacecraft to enter orbit around two different target worlds.

Read more: Find Out How “Crazy Engineering” is Getting Dawn to Ceres

Learn more at JPL’s Dawn mission site here, and find out where Dawn is right now here.

Also, read more from the Max Planck Institute for Solar System Research here.

Source: NASA/MPI

Posted on by Elizabeth Howell

Surprise! Asteroid Crashes And Raindrop Splashes Look Almost Alike

Close-up view of a raindrop falling on a granular surface, which produces effects similar to an asteroid collision (but on a much smaller scale). Credit: Xiang Cheng, University of Minnesota et al./APS Physics/YouTube (screenshot)

It’s hard to study what an asteroid impact does real-time as you’d need to be looking at the right spot at the right time. So simulations are often the way to go. Here’s a fun idea captured on video — throwing drops of water on to granular particles, similar to what you would find on a beach. The results, the researchers say, look surprisingly similar to “crater morphology”.

A quick caution — the similarity isn’t completely perfect. Raindrops are much smaller, and hit the ground at quite a lower speed than you would see an asteroid slam into Earth’s surface. But as the authors explain in a recent abstract, there is enough for them to do high-speed photography and make extrapolations.

Although the mechanism of granular impact cratering by solid spheres is well explored, our knowledge on granular impact cratering by liquid drops is still very limited. Here, by combining high-speed photography with high-precision laser profilometry, we investigate liquid-drop impact dynamics on granular surface and monitor the morphology of resulting impact craters. Surprisingly, we find that despite the enormous energy and length difference, granular impact cratering by liquid drops follows the same energy scaling and reproduces the same crater morphology as that of asteroid impact craters.

There are of course other ways of understanding how craters are formed. A common one is to look at them in “airless” bodies such as the Moon, Vesta or Ceres — and that latter world will be under extensive study in the next year. NASA’s Dawn spacecraft is en route to the dwarf planet right now and will arrive there in 2015 to provide the first high-resolution views of its surface.

Amateurs can even collaborate with professionals in this regard by participating in Cosmoquest, an organization that hosts Moon Mappers, Planet Mappers: Mercury and Asteroid Mappers: Vesta — all examples of bodies in a vacuum with craters on them.

The research was presented at the APS Division of Fluid Dynamics annual meeting and published in the Proceedings of the National Academy of Sciences. It was led by Runchen Zhao at the University of Minnesota.

Posted on by Elizabeth Howell

Dawn Spacecraft’s Dwarf Planet Dance Improves Hubble’s Far-Away View

Vesta seen from the Earth-orbit based Hubble Space Telescope in 2007 (left) and up close with the Dawn spacecraft in 2011. Hubble Credit: NASA, ESA, and L. McFadden (University of Maryland). Dawn Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Photo Combination: Elizabeth Howell

The Hubble Space Telescope is one of the best observatories humanity has. It’s been operating for nearly 25 years in space, is still highly productive, and is a key element to mission planning for NASA as it sends spacecraft out into the Solar System. When the agency was getting ready to send Dawn to Vesta, for example, it took pictures to help with calibration.

Then Dawn got up close to the dwarf planet in 2011 and found a few surprises — liquid water that possibly flowed temporarily on the surface, for example. And as the spacecraft draws near to Ceres for a close encounter next year, it also will be looking for water — in the form of its atmosphere.

That’s following on from research out of the Herschel Space Telescope published earlier this year, showing that Ceres has a thin water vapor atmosphere surrounding the dwarf planet. It could be producing water similarly to how a comet does, through sublimation, but investigators won’t know much until they get close-up.

“Ceres has some sort of mechanism that’s putting out water vapor and causing a thin, temporary atmosphere,” said Keri Bean, a mission operations engineer at the Jet Propulsion Laboratory who works on Dawn, in a Google+ Hangout yesterday (Dec. 11). “I think that we’re going to try to look into this, and we don’t know what else Ceres will have in store for us.”

Ceres as seen from the Earth-based Hubble Space Telescope in 2004 (left) and with the Dawn spacecraft in 2014 as it approached the dwarf planet. Hubble Credit: NASA, ESA, J. Parker (Southwest Research Institute), P. Thomas (Cornell University), L. McFadden (University of Maryland, College Park), and M. Mutchler and Z. Levay (STScI). Dawn Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Photo Combination: Elizabeth Howell
Ceres as seen from the Earth-based Hubble Space Telescope in 2004 (left) and with the Dawn spacecraft in 2014 as it approached the dwarf planet. Hubble Credit: NASA, ESA, J. Parker (Southwest Research Institute), P. Thomas (Cornell University), L. McFadden (University of Maryland, College Park), and M. Mutchler and Z. Levay (STScI). Dawn Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA. Photo Combination: Elizabeth Howell

Dawn is now so close to Ceres that its pictures will soon exceed the best ones Hubble had to offer. The image above (at right) is modest compared to the space telescope, but in a planned photo session Jan. 26 Dawn will have slightly better pictures than Hubble. By Feb. 4 they will be twice as good in quality and then seven times as good Feb. 20.

The spacecraft’s images not only have science purposes, as they let investigators study the surface, but also serve as optical navigation aids. Ceres is a tiny body and hard to navigate to from far away, so as it gets closer these pictures are crucial for Dawn to figure out where to go next.

Dawn will get its close-up of Ceres in the spring when it arrives at the dwarf planet. To get the latest on the mission, check out the entire Google+ Hangout from yesterday.

Posted on by Elizabeth Howell

Dawn Spacecraft Will Take Pictures Of Its Target Dwarf Planet Today

Artist's conception of the Dawn spacecraft approaching the asteroid Ceres. Credit: NASA/JPL-Caltech

The year 2015 is going to be a big one for far-off spacecraft. Among them is the long-running Dawn mission, which is on its way to the dwarf planet Ceres (by way of Vesta) and should settle into orbit in April after a radiation blast delayed the original flight plan.

And today (Dec. 1) comes a special day for Dawn — when it turns its cameras to Ceres to capture the world, which will appear about nine pixels across. The reason? Besides scientific curiosity, it turns out to be a perfect calibration target, according to NASA.

“One final calibration of the science camera is needed before arrival at Ceres,” wrote Marc Rayman, the mission director at the Jet Propulsion Laboratory, in a recent blog post.

“To accomplish it, the camera needs to take pictures of a target that appears just a few pixels across. The endless sky that surrounds our interplanetary traveler is full of stars, but those beautiful pinpoints of light, while easily detectable, are too small for this specialized measurement. But there is an object that just happens to be the right size. On Dec. 1, Ceres will be about nine pixels in diameter, nearly perfect for this calibration.”

The Dawn spacecraft's first image of Ceres, taken July 20, 2010. Credit: NASA/JPL-Caltech/MPS/DLR/IDA
The Dawn spacecraft’s first image of Ceres, taken July 20, 2010. Credit: NASA/JPL-Caltech/MPS/DLR/IDA

This isn’t the first picture of Ceres by Dawn — not by a long-shot — but it sure will loom bigger than you see in the image at left, which was taken in 2010. Dawn hadn’t even arrived at Vesta at the time, the blog post points out, and the spacecraft was about 1,300 times further from Ceres then as it is now. Translating that into visual magnitude, the new pictures of Ceres will show an appearance about as bright as Venus, from Earth’s perspective.

In October, the Dawn blog said that more pictures of Ceres are planned on Jan. 13, when Ceres will appear 25 pixels across. This won’t be quite the best view ever — that was taken by the Hubble Space Telescope, which you can see below, — but just wait a couple of weeks. The mission planners say that by Jan. 26, the images will be slightly better. On Feb. 4, they will be twice as good and by Feb. 20, seven times as good.

As with the calibration photo taken today, these photos in 2015 will have a double purpose: optical navigation. It’s to help the spacecraft figure out where to go, because our pictures of Ceres are so fuzzy that mission planners will need more exact information as the mission proceeds.

You can read more information about the picture-taking, and Dawn’s planned approach to Ceres, in the Nov. 28 entry of the Dawn blog.

Pictures of the asteroid Ceres taken by the Hubble Space Telescope and released in 2005. It shows the asteroid moving over two hours and 20 minutes, which is about a quarter of a day on Ceres (nine hours). At the time, scientists said the bright spot is a mystery. Credit: NASA, ESA, J. Parker (Southwest Research Institute), P. Thomas (Cornell University), and L. McFadden (University of Maryland, College Park)
Pictures of the asteroid Ceres taken by the Hubble Space Telescope and released in 2005. It shows the asteroid rotating over two hours and 20 minutes, which is about a quarter of a day on Ceres (nine hours). At the time, scientists said the bright spot is a mystery. Credit: NASA, ESA, J. Parker (Southwest Research Institute), P. Thomas (Cornell University), and L. McFadden (University of Maryland, College Park)
Posted on by Matt Williams

Amazingly Detailed New Maps of Asteroid Vesta

Artist's concept of the Dawn spacecraft arriving at Vesta. Image credit: NASA/JPL-Caltech

Vesta is one of the largest asteroids in the Solar System. Comprising 9% of the mass in the Asteroid Belt, it is second in size only to the dwarf-planet Ceres. And now, thanks to data obtained by NASA’s Dawn spacecraft, Vesta’s surface has been mapped out in unprecedented detail.
These high-resolution geological maps reveal the variety of Vesta’s surface features and provide a window into the asteroid’s history.

“The geologic mapping campaign at Vesta took about two-and-a-half years to complete, and the resulting maps enabled us to recognize a geologic timescale of Vesta for comparison to other planets,” said David Williams of Arizona State University.

Geological mapping is a technique used to derive the geologic history of a planetary object from detailed analysis of surface morphology, topography, color and brightness information. The team found that Vesta’s geological history is characterized by a sequence of large impact events, primarily by the Veneneia and Rheasilvia impacts in Vesta’s early history and the Marcia impact in its late history.

The geologic mapping of Vesta was made possible by the Dawn spacecraft’s framing camera, which was provided by the Max Planck Institute for Solar System Research of the German Max Planck Society and the German Aerospace Center.  This camera takes panchromatic images and seven bands of color-filtered images, which are used to create topographic models of the surface that aid in the geologic interpretation.

A team of 14 scientists mapped the surface of Vesta using Dawn data. The study was led by three NASA-funded participating scientists: Williams; R. Aileen Yingst of the Planetary Science Institute; and W. Brent Garry of the NASA Goddard Spaceflight Center.

This high-res geological map of Vesta is derived from Dawn spacecraft data. Brown colors represent the oldest, most heavily cratered surface. Credit: NASA/JPL-Caltech/ASU
This high-res geological map of Vesta is derived from Dawn spacecraft data. Credit: NASA/JPL-Caltech/ASU

The brown colored sections of the map represent the oldest, most heavily cratered surface. Purple colors in the north and light blue represent terrains modified by the Veneneia and Rheasilvia impacts, respectively. Light purples and dark blue colors below the equator represent the interior of the Rheasilvia and Veneneia basins. Greens and yellows represent relatively young landslides or other downhill movement and crater impact materials, respectively.

The map indicates the prominence of impact events – such as the Veneneia, Rheasilvia and Marcia impacts, respectively – in shaping the asteroid’s surface. It also indicates that the oldest crust on Vesta pre-dates the earliest Veneneia impact. The relative timescale is supplemented by model-based absolute ages from two different approaches that apply crater statistics to date the surface.

“This mapping was crucial for getting a better understanding of Vesta’s geological history, as well as providing context for the compositional information that we received from other instruments on the spacecraft: the visible and infrared (VIR) mapping spectrometer and the gamma-ray and neutron detector (GRaND),” said Carol Raymond, Dawn’s deputy principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, California.

The objective of NASA’s Dawn mission is to characterize the two most massive objects in the main asteroid belt between Mars and Jupiter – Vesta and the dwarf planet Ceres.

These Hubble Space Telescope images of Vesta and Ceres show two of the most massive asteroids in the asteroid belt, a region between Mars and Jupiter. Credit: NASA/European Space Agency
These Hubble Space Telescope images of Vesta and Ceres show two of the most massive asteroids in the asteroid belt. Credit: NASA/European Space Agency

Asteroids like Vesta are remnants of the formation of the solar system, giving scientists a peek at its early history. They can also harbor molecules that are the building blocks of life and reveal clues about the origins of life on Earth. Hence why scientists are eager to learn more about its secrets.

The Dawn spacecraft was launched in September of 2007 and orbited Vesta between July 2011 and September 2012. Using ion propulsion in spiraling trajectories to travel from Earth to Vesta, Dawn will orbit Vesta and then continue on to orbit the dwarf planet Ceres by April 2015.

The high resolution maps were included with a series of 11 scientific papers published this week in a special issue of the journal Icarus. The Dawn spacecraft is currently on its way to Ceres, the largest object in the asteroid belt, and will arrive at Ceres in March 2015.

Further Reading: NASA

Posted on by Jason Major

How an Ancient Angled Impact Created Vesta’s Groovy Belt

Vivid Vesta Vista in Vibrant 3 D from NASA’s Dawn Asteroid Orbiter. Vesta is the second most massive asteroid and is 330 miles (530 km) in diameter. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

When NASA’s Dawn spacecraft arrived at Vesta in July 2011, two features immediately jumped out at planetary scientists who had been so eagerly anticipating a good look at the giant asteroid. One was a series of long troughs encircling Vesta’s equator, and the other was the enormous crater at its southern pole. Named Rheasilvia, the centrally-peaked basin spans 500 kilometers in width and it was hypothesized that the impact event that created it was also responsible for the deep Grand Canyon-sized grooves gouging Vesta’s middle.

Now, research led by a Brown University professor and a former graduate student reveal how it all probably happened.

“Vesta got hammered,” said Peter Schultz, professor of earth, environmental, and planetary sciences at Brown and the study’s senior author. “The whole interior was reverberating, and what we see on the surface is the manifestation of what happened in the interior.”

Using a 4-meter-long air-powered cannon at NASA’s Ames Vertical Gun Range, Peter Schultz and Brown graduate Angela Stickle – now a researcher at the Johns Hopkins University Applied Physics Laboratory – recreated cosmic impact events with small pellets fired at softball-sized acrylic spheres at the type of velocities you’d find in space.

The impacts were captured on super-high-speed camera. What Stickle and Schultz saw were stress fractures occurring not only at the points of impact on the acrylic spheres but also at the point directly opposite them, and then rapidly propagating toward the midlines of the spheres… their “equators,” if you will.

Scaled up to Vesta size and composition, these levels of forces would have created precisely the types of deep troughs seen today running askew around Vesta’s midsection.

Watch a million-fps video of a test impact below:

So why is Vesta’s trough belt slanted? According to the researchers’ abstract, “experimental and numerical results reveal that the offset angle is a natural consequence of oblique impacts into a spherical target.” That is, the impactor that struck Vesta’s south pole likely came in at an angle, which made for uneven propagation of stress fracturing outward across the protoplanet (and smashed its south pole so much that scientists had initially said it was “missing!”)

Close-ups of Vesta's equatorial troughs obtained by Dawn's framing camera in August and September 2011. (NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA)
Close-ups of Vesta’s equatorial troughs obtained by Dawn’s framing camera in August and September 2011. (NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA)

That angle of incidence — estimated to be less than 40 degrees — not only left Vesta with a slanted belt of grooves, but also probably kept it from getting blasted apart altogether.

“Vesta was lucky,” said Schultz. “If this collision had been straight on, there would have been one less large asteroid and only a family of fragments left behind.”

Watch a video tour of Vesta made from data acquired by Dawn in 2011 and 2012 below:

The team’s findings will be published in the February 2015 issue of the journal Icarus and are currently available online here (paywall, sorry). Also you can see many more images of Vesta from the Dawn mission here and find out the latest news from the ongoing mission to Ceres on the Dawn Journal.

Source: Brown University news