Dwarf Planets: Science and Facts

Pluto was demoted to dwarf planet status in 2006, joining Eris, Haumea, Makemake and Ceres.

Credit: Karl Tate, SPACE.com

In 2006, an assembly of the International Astronomical Union voted to define a planet as a celestial body that a) is in orbit around the sun, 2) has enough mass for its gravity to pull it into a rounded shape (hydrostatic equilibrium), and 3) has cleared the neighborhood of its orbit of other, smaller objects.

This last criterion is the point at which planets and dwarf planets differ. A planet's gravity either attracts or pushes away the smaller bodies that would otherwise intersect its orbit; the gravity of a dwarf planet is not sufficient to make this happen.

Astronomers estimate that there could be as many as 200 dwarf planets in the solar system and Kuiper Belt. But the differences between planets and dwarf planets may not be obvious at first. 

NASA DAWN: New Images of CERES - Animation

This image is one several images NASA's Dawn spacecraft took on approach to Ceres on Feb. 4, 2015 at a distance of about 90,000 miles (145,000 kilometers) from the dwarf planet. 

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

NASA's Dawn spacecraft, on approach to dwarf planet Ceres, has acquired its latest and closest-yet snapshot of this mysterious world.

The above image of Ceres, taken on Feb. 4, 2015, from a distance of about 90,000 miles (145,000 kilometers).

At a resolution of 8.5 miles (14 kilometers) per pixel, the pictures represent the sharpest images to date of Ceres.

After the spacecraft arrives and enters into orbit around the dwarf planet, it will study the intriguing world in great detail.

Ceres, with a diameter of 590 miles (950 kilometers), is the largest object in the main asteroid belt, located between Mars and Jupiter.

NASA DAWN: Mysterious Bright Spot on Dwarf Planet Ceres

A mysterious white spot can be seen in the newest images from NASA's Dawn spacecraft, which is rapidly approaching the dwarf planet. 

Credit: NASA /JPL-Caltech /UCLA /MPS /DLR /IDA /PSI

A strange, flickering white blotch found on the dwarf planet Ceres by NASA's Dawn spacecraft has scientists scratching their heads.

The white spot on Ceres in a series of new photos taken on Jan. 13 by NASA's Dawn spacecraft, which is rapidly approaching the round dwarf planet in the asteroid belt between the orbits of Mars and Jupiter, but when the initial photo release on Monday (Jan. 19), the Dawn scientists gave no indication of what the white dot might be.

"Yes, we can confirm that it is something on Ceres that reflects more sunlight, but what that is remains a mystery," Marc Rayman, mission director and chief engineer for the Dawn mission, told Space.com in an email.




The new images show areas of light and dark on the face of Ceres, which indicate surface features like craters, but at the moment, none of the specific features can be resolved, including the white spot.

"We do not know what the white spot is, but it's certainly intriguing," Rayman said. "In fact, it makes you want to send a spacecraft there to find out, and of course that is exactly what we are doing! So as Dawn brings Ceres into sharper focus, we will be able to see with exquisite detail what [the white spot] is."

Ceres is a unique object in our solar system. It is the largest object in the asteroid belt and is classified as an asteroid. It is simultaneously classified as a dwarf planet, and at 590 miles across (950 kilometers, or about the size of Texas), Ceres is the smallest known dwarf planet in the solar system.

The $466 million Dawn spacecraft is set to enter into orbit around Ceres on March 6. Dawn left Earth in 2007 and in the summer of 2011, it made a year-long pit stop at the asteroid Vesta, the second largest object in the asteroid belt.

NASA Dawn Spacecraft captures new images of CERES craters

The Dawn spacecraft observed Ceres for an hour on Jan. 13, 2015, from a distance of 238,000 miles (383,000 kilometers). 

A little more than half of its surface was observed at a resolution of 27 pixels. 

This animated GIF shows bright and dark features. 

Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

Latest image from Nasa's Dawn Spacecraft showing the craters on Ceres.

Credit: NASA

NASA's Dawn spacecraft has entered an approach phase in which it will continue to close in on Ceres, a Texas-sized dwarf planet never before visited by a spacecraft.

Dawn launched in 2007 and is scheduled to enter Ceres orbit in March 2015.

Dawn recently emerged from solar conjunction, in which the spacecraft is on the opposite side of the sun, limiting communication with antennas on Earth.

Now that Dawn can reliably communicate with Earth again, mission controllers have programmed the maneuvers necessary for the next stage of the rendezvous, which they label the Ceres approach phase.

Dawn is currently 400,000 miles (640,000 kilometers) from Ceres, approaching it at around 450 miles per hour (725 kilometers per hour).

The spacecraft's arrival at Ceres will mark the first time that a spacecraft has ever orbited two solar system targets.

NASA New Horizon Mission 2015, the year of the Dwarf Planet

This “movie” of Pluto and its largest moon, Charon, by NASA’s New Horizons spacecraft taken in July 2014 clearly shows that the barycenter, the centre of mass of the two bodies, resides outside (between) both bodies. 

The 12 images that make up the movie were taken by the spacecraft’s best telescopic camera, the Long Range Reconnaissance Imager (LORRI), at distances ranging from about 267 million to 262 million miles (429 million to 422 million kilometers). 

Charon is orbiting approximately 11,200 miles (about 18,000 kilometers) above Pluto’s surface. 

Credit: NASA /Johns Hopkins University Applied Physics Laboratory /Southwest Research Institute

The New Horizons mission became the first mission of NASA's New Frontiers program, beginning development in 2001.

The probe was launched on January 19, 2006, atop an Atlas V 551 (5 solid rocket boosters plus a third stage).

Utilising more compact and lightweight electronics than its predecessors to the outer planets, Pioneer 10 & 11, and Voyager 1 & 2, the combination of reduced weight, a powerful launch vehicle, plus a gravity assist from Jupiter has lead to a nine year journey.

On December 6, 2014, New Horizons was taken out of hibernation for the last time and now remains powered on until the Pluto encounter.

The arrival date of New Horizon is July 14, 2015. A telescope called the Long Range Reconnaissance Imager (LORRI) has permitted the commencement of observations while still over 240 million kilometers (150 million miles) from Pluto.

The first stellar-like images were taken while still in the Asteroid belt in 2006.

NASA Dawn Spacecraft Begins Approach to Ceres

NASA's Dawn spacecraft has entered an approach phase in which it will continue to close in on Ceres, a Texas-sized dwarf planet never before visited by a spacecraft. Dawn launched in 2007 and is scheduled to enter Ceres orbit in March 2015.

Dawn recently emerged from solar conjunction, in which the spacecraft is on the opposite side of the sun, limiting communication with antennas on Earth.

Now that Dawn can reliably communicate with Earth again, mission controllers have programmed the maneuvers necessary for the next stage of the rendezvous, which they label the Ceres approach phase.

Dawn is currently 400,000 miles (640,000 kilometers) from Ceres, approaching it at around 450 miles per hour (725 kilometers per hour).

The spacecraft's arrival at Ceres will mark the first time that a spacecraft has ever orbited two solar system targets.

Dawn previously explored the protoplanet Vesta for 14 months, from 2011 to 2012, capturing detailed images and data about that body.

"Ceres is almost a complete mystery to us," said Christopher Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles.

"Ceres, unlike Vesta, has no meteorites linked to it to help reveal its secrets. All we can predict with confidence is that we will be surprised."

The two planetary bodies are thought to be different in a few important ways. Ceres may have formed later than Vesta, and with a cooler interior.

Current evidence suggests that Vesta only retained a small amount of water because it formed earlier, when radioactive material was more abundant, which would have produced more heat.

Ceres, in contrast, has a thick ice mantle and may even have an ocean beneath its icy crust.

The two planetary bodies are thought to be very different. Ceres has an average diameter of 950 km (590 miles) while Vesta has an average diameter of 525 km (326 miles).

Ceres may have formed later than Vesta, and have a cooler interior. Vesta formed earlier, when radioactive material was more abundant, which produced more heat so Vesta retained little water, whereas Ceres has a thick ice mantle and may even have an ocean beneath its icy crust.

Dawn is currently 640,000 km (400,000 miles) from Ceres, approaching it at around 725 km per hour (450 miles per hour).

Ceres is also the largest body in the asteroid belt, the strip of solar system real estate between Mars and Jupiter.

By comparison, Vesta has an average diameter of 326 miles (525 kilometers), and is the second most massive body in the belt.

The spacecraft uses ion propulsion to traverse space far more efficiently than if it used chemical propulsion. In an ion propulsion engine, an electrical charge is applied to xenon gas, and charged metal grids accelerate the xenon particles out of the thruster.

These particles push back on the thruster as they exit, creating a reaction force that propels the spacecraft. Dawn has now completed five years of accumulated thrust time, far more than any other spacecraft.

"Orbiting both Vesta and Ceres would be truly impossible with conventional propulsion. Thanks to ion propulsion, we're about to make history as the first spaceship ever to orbit two unexplored alien worlds," said Marc Rayman, Dawn's chief engineer and mission director, based at NASA's Jet Propulsion Laboratory in Pasadena, California.

The next couple of months promise continually improving views of Ceres, prior to Dawn's arrival. By the end of January, the spacecraft's images and other data will be the best ever taken of the dwarf planet.

France Proceeding with Next Generation Communications despite budget cuts

French officials continue to debate whether to outsource the nation’s next-generation Syracuse military telecommunications system (above, Syracuse 3A satellite) to the private sector, as has been done in Britain and, to a lesser extent, in Italy and Germany; or to proceed with a conventional procurement. 

Credit: Thales Alenia artist's concept

The French Defense Ministry on Oct. 1 said its planned electronic-intelligence satellite and next-generation military telecommunications satellite systems have survived a rough arbitrage of France’s budget and would be under contract in 2015.

The budget package outlined Oct. 1 does not specify cost amounts. It further suggests that the Defense Ministry may have recourse to a sale-and-leaseback formula to generate near-term cash that will help meet the requirements of its priority programs.

Dossier Information

French officials continue to debate whether to outsource the nation’s next-generation Thales Syracuse military telecommunications system to the private sector, as has been done in Britain and, to a lesser extent, in Italy and Germany; or to proceed with a conventional procurement.

France has also been talking with Italian and British military planners about combining at least part of their future military satellite communications needs, perhaps with a jointly owned satellite that would act as a backup for these nations’ primary satellite telecommunications assets.

Meanwhile, France’s Ceres electronic-intelligence satellite system, planned as three spacecraft flying in formation in low Earth orbit, has been a French priority for several years but has struggled for traction in a harsh budget environment.

Here is a translated extract from the French Finance Bill 2014 "The program CERES 20 is to have an operational capacity to listen, that could allow the interception and location of electromagnetic emissions from space (detection and radar transmitters or telecommunications location). This need was formalized through the launch of the preparation stage of the operation CERES, June 27, 2007. The system cost is estimated at around 460 million euros."

"The financial effort applied to the French Ministry of Defence at work 2011-2013 triennial budget planning has resulted in a shift of the CERES program. Planning now assumes an operational implementation in 2020."

Adding to the problem has been France’s inability to interest other European nations in joining Ceres.

"In autumn 2007, the EMA and the DGA jointly proposed to the countries cooperating MUSIS, as well as Sweden and Switzerland to join the operation CERES. Only Greece and Sweden have responded positively to the preparatory work and contributed financially. At the end of the work, in May 2011, Sweden announced it would terminate its participation for budgetary reasons."

Airbus Defence and Space (EADS) and Thales Alenia Space, Europe’s two biggest satellite manufacturers, which both have a large presence in France, are already under contract for initial Ceres studies.

Both have also expressed interest in managing the future military telecommunications satellite program with France as the anchor customer.

NASA Dawn back on course after briefly slipping into Safe Mode

NASA's Dawn spacecraft has resumed normal operations after a high-energy particle event forced the mission to enter safe mode, knocking its ion drive offline.

Although mission managers deduced the source of the problem and restarted its propulsion systems, the unexpected hiccup will likely delay Dawn’s arrival at dwarf planet Ceres.

Safe mode was triggered on Sept. 11 and it is thought the same phenomenon that triggered a safe mode three years agoduring Dawn's approach to giant asteroid Vesta is to blame for this incident.

A high-energy cosmic ray hit the spacecraft's ion drive electronics, disabling it.

In addition to the ion drive glitch, Dawn's main antennae that the spacecraft uses to communicate with Earth was also knocked offline, meaning engineers had to decipher the problem using Dawn’s secondary, lower bandwidth antennae.

"This anomaly presented the team with an intricate and elaborate puzzle to solve," said Robert Mase, Dawn project manager at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif.

"We followed the same strategy that we implemented three years ago to recover from a similar radiation strike, to swap to one of the other ion engines and a different electronic controller so we could resume thrusting quickly," said Dawn Mission Director and Chief Engineer Marc Rayman also of JPL.

“We have a plan in place to revive this disabled component later this year.”

NASA DAWN: Spacecraft operating normally after safe mode triggered

Artist concept of NASA's Dawn spacecraft orbiting Ceres during an upcoming flyby. 

Credit: NASA/JPL-Caltech/UCLA

The Dawn spacecraft has resumed normal ion thrusting after the thrusting unexpectedly stopped and the spacecraft entered safe mode on September 11.

That anomaly occurred shortly before a planned communication with NASA's Deep Space Network that morning.

The spacecraft was not performing any special activities at the time.

Engineers immediately began working to restore the spacecraft to its normal operational state.

The team determined the source of the problems, corrected them, and then resumed normal ion thrusting on Monday night, Sept. 15.

"This anomaly presented the team with an intricate and elaborate puzzle to solve," said Robert Mase, Dawn project manager at NASA's Jet Propulsion Laboratory in Pasadena, California.

After investigating what caused the spacecraft to enter safe mode, the Dawn team determined that it was likely triggered by the same phenomenon that affected Dawn three years ago on approach to the protoplanet Vesta: An electrical component in the ion propulsion system was disabled by a high-energy particle of radiation.

"We followed the same strategy that we implemented three years ago to recover from a similar radiation strike, to swap to one of the other ion engines and a different electronic controller so we could resume thrusting quickly," said Dawn Mission Director and Chief Engineer Marc Rayman of JPL.

"We have a plan in place to revive this disabled component later this year."

Complicating the issue, the team discovered that the spacecraft had experienced not just one anomaly, but also a second one that affected the ability to point the main antenna at Earth to communicate.

Because the spacecraft could not communicate using its main antenna, the team had to utilize the weaker signals of another antenna, slowing their progress.

In addition, Dawn is so far from Earth that radio signals take 53 minutes to make the round trip.

Although they have not yet specifically pinpointed the cause of this issue, it could also be explained by a high-energy particle corrupting the software running in the main computer.

Ultimately the team reset the computer, which restored the pointing performance to normal.

As a result of the change in the thrust plan, Dawn will enter into orbit around dwarf planet Ceres in April 2015, about a month later than previously planned.

Ceres

The plans for exploring Ceres once the spacecraft is in orbit, however, are not affected.

Vesta

Dawn orbited Vesta, the second most massive object in the main asteroid belt, from July 2011 until September 2012.

The spacecraft's ion propulsion system enabled it to spiral away from Vesta and head toward Ceres, the most massive object in that region.

NASA's Curiosity rover captures images of asteroids Ceres and Vesta

For the first time, NASA's Curiosity rover has captured images of an asteroid from the surface of Mars -- two of them, in fact.

The imagery recorded by Curiosity and beamed back to Earth feature Ceres and Vesta, two of the largest asteroids in the asteroid belt that runs between between Mars and Jupiter.

This Curiosity first was also a bit of a coincidence, as the SUV-sized rover had aimed its cameras at the Martian sky in order to snap shots of the Red Planet's two moons, not hunt for asteroids whizzing by.

"This imaging was part of an experiment checking the opacity of the atmosphere at night in Curiosity's location on Mars, where water-ice clouds and hazes develop during this season," camera team member Mark Lemmon, of Texas A&M University, explained in a statement.

"The two Martian moons were the main targets that night, but we chose a time when one of the moons was near Ceres and Vesta in the sky."

Mark Lemmon

NASA is currently on its way to get an even closer look at this two giant space rocks.

NASA's Dawn spacecraft orbited the 350-mile-wide Vesta asteroid in 2011 and 2012, and it is preparing to orbit the 590-mile-wide Ceres in 2015.

NASA Dawn creates guide to Vesta's hidden attractions

This colorful composite image from NASA's Dawn mission shows the flow of material inside and outside a crater called Aelia on the giant asteroid Vesta. 

The area is around 14 degrees south latitude. 

The images that went into this composite were obtained by Dawn's framing camera from September to October 2011.

Credit: NASA /JPL-Caltech /UCLAMPS /DLR /IDA

Some beauty is revealed only at a second glance. When viewed with the human eye, the giant asteroid Vesta, which was the object of scrutiny by the Dawn spacecraft from 2011 to 2012, is quite unspectacular color-wise. Vesta looks grayish, pitted by a variety of large and small craters.

But scientists at the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany, have re-analyzed the images of this giant asteroid obtained by Dawn's framing camera.

They assigned colors to different wavelengths of light and, in the process, revealed in unprecedented detail not only geological structures that are invisible to the naked eye, but also landscapes of incomparable beauty.

Researchers at Max Planck can now see structures such as melts from impacts, craters buried by quakes and foreign material brought by space rocks, visible with a resolution of 200 feet (60 meters) per pixel.

"The key to these images is the seven color filters of the camera system on board the spacecraft," said Andreas Nathues, the framing camera team lead at Max Planck."

"Since different minerals reflect light of different wavelengths to different degrees, the filters help reveal compositional differences that remain hidden without them. In addition, scientists calibrated the data so that the finest variations in brightness can be seen.

This coloured composite image from NASA's Dawn mission shows the crater Antonia, which lies in the enormous Rheasilvia basin in the southern hemisphere of the giant asteroid Vesta. 

The area lies around 58 degrees south latitude. 

Antonia has a diameter of 11 miles (17 kilometers). 

Credit: NASA/JPL-Caltech/UCLAMPS/DLR/IDA

In the new colorized images, different colors indicate different materials on the surface of Vesta. They reveal impressive formations and a wide range of geological diversity, said Nathues. But above all, the color-coded images are impressive because of their beauty.

"No artist could paint something like that. Only nature can do this," said Martin Hoffman, a member of the framing camera team also at Max Planck.

Pictures of the crater Aelia, the crater Antonia and an area near the crater Sextilia show some of Vesta's most impressive sites.

This colorful image from NASA's Dawn mission shows material northwest of the crater Sextilia on the giant asteroid Vesta. 

Sextilia, located around 30 degrees south latitude, is at the bottom right of this image. 

Credit: NASA/JPL-Caltech/UCLAMPS/DLR/IDA

Dawn visited Vesta from July 2011 to September 2012. The spacecraft is currently on its way to its second destination, the dwarf planet Ceres.

Ceres is the largest object in the main asteroid belt between Mars and Jupiter.

NASA DAWN: Ice on Ceres is an 'Interesting Paradox'

Hubble Space Telescope imaged the asteroid Vesta and the dwarf planet Ceres in 2007, both targets of NASA's Dawn mission. 

Credit: NASA, ESA, J. Parker (SwRI), L. McFadden (U Maryland)

As NASA's Dawn mission draws closer to its encounter with the dwarf planet Ceres in early 2015, excitement continues to mount for scientists looking forward to what the satellite might observe.

Britney Schmidt

Britney Schmidt, of the George Institute of Technology, and Nicole Gugliucci of CosmoQuest, recently hosted a Google+ Hangout titled 'Ceres: Great Expectations' to discuss the upcoming visit to the nearest dwarf planet in the solar system.

Orbiting in the asteroid belt, a little more than three times as far from the Sun as Earth, Ceres is thought to contain an icy mantle that makes up approximately a third of its mass.

"Ceres is very different and very exciting in a lot of ways, totally different from any place that we've been," Schmidt said in the broadcast. "It may be the only primarily icy planet that's out there, at least within reach."

Scratching the surface
Seen through a telescope, Ceres may not appear very exciting.

Scientists can use the light reflected off of a body to find out information about its composition.

"Ceres, to the eye, would appear basically pretty black because it's reflecting most colours more or less the same, and reflecting very little light at all," said Andy Rivkin of the Johns Hopkins University Applied Physics Lab.

Andy Rivkin

Even the infrared spectrum, which tends to reveal more information about asteroids such as Vesta—Dawn's first stop—provided very little information about its composition.

By utilizing instruments such as the SpeX instrument on the NASA Infrared Telescope Facility (IRTF) on Mauna Kea in Hawaii, scientists were able to catch hints about the dwarf planet's surface.

These observations revealed suggestions of brucite, hydroxyls, and two other features Rivkin says are thought to be due to carbonate minerals.

"[This] makes Ceres one of only a few places where we've found carbonates," Rivkin said. "I think other than Earth and Mars, it's Ceres."

He went on to explain that scientists think water interacting with the minerals formed the brucite and the carbonates.

The layers of Ceres. Scientists think that the dwarf planet contains a rocky inner core surrounded by a thick mantle of water-ice. 

A thin outer crust covers the surface, with carbonates and other signs that water lay on the planet's skin at some point. 

Credit: NASA, ESA, and A. Feild (STScI)

"For Ceres, we think it is much more consistent with a body that had a lot of water available to interact with."

But water, considered a potential habitat for life to start, can't exist on the surface of the dwarf planet in either solid or liquid form.

"We see no real evidence for ice at the surface of Ceres," Rivkin said, noting that the dwarf planet is too warm. "However, conditions beneath Ceres' surface should allow buried ice to remain there."

At the same time, observations from the Hubble Space Telescope, as well as theoretical data such as the planet's density, suggest that a large amount of ice exists.

"That creates this interesting paradox. We think there's a lot of ice there, (but) we don't see any at the surface," Rivkin said.

"How that's going to translate into what we find when we show up there is still very much an open question."

NASA DAWN readied for engagement with CERES

This artist's concept shows NASA's Dawn spacecraft heading toward the dwarf planet Ceres. 

Dawn spent nearly 14 months orbiting Vesta, the second most massive object in the main asteroid belt between Mars and Jupiter, from 2011 to 2012.

It is heading towards Ceres, the largest member of the asteroid belt.

When Dawn arrives, it will be the first spacecraft to go into orbit around two destinations in our solar system beyond Earth. 

Image credit: NASA/JPL-Caltech

NASA's Dawn spacecraft is ready to engage with dwarf planet Ceres, and mission managers have stated.

Dawn has been cruising toward Ceres, the largest object in the main asteroid belt between Mars and Jupiter, since September 2012, when it departed from its other target, Vesta.

Ceres presents an icy—possibly watery—counterpoint to the dry Vesta, where Dawn spent almost 14 months.

Vesta and Ceres are two of the largest surviving protoplanets—bodies that almost became planets—and will give scientists clues about the planet-forming conditions at the dawn of our solar system.

When Dawn enters orbit around Ceres, it will be the first spacecraft to see a dwarf planet up-close and the first spacecraft to orbit two solar system destinations beyond Earth.

"Our flight plan around Ceres will be choreographed to be very similar to the strategy that we successfully used around Vesta," said Bob Mase, Dawn's project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

"This approach will build on that and enable scientists to make direct comparisons between these two giants of the asteroid belt."

As a prelude, the team will begin approach operations in late January 2015. The next month, Ceres will be big enough in Dawn's view to be imaged and used for navigation purposes.

Dawn will arrive at Ceres—or, more accurately, it will be captured by Ceres' gravity—in late March or the beginning of April 2015.

NASA's Dawn spacecraft will be getting an up-close look at the dwarf planet Ceres starting in late March or the beginning of April 2015. 

This graphic shows the science-gathering orbits planned for the spacecraft, with the altitudes above the surface noted for each of the orbits. 

Credit: NASA/JPL-Caltech

Dawn will make its first full characterization of Ceres later in April, at an altitude of about 8,400 miles (13,500 kilometers) above the icy surface.

Then, it will spiral down to an altitude of about 2,750 miles (4,430 kilometers), and obtain more science data in its survey science orbit.

This phase will last for 22 days, and is designed to obtain a global view of Ceres with Dawn's framing camera, and global maps with the visible and infrared mapping spectrometer (VIR).

Dawn will then continue to spiral its way down to an altitude of about 920 miles (1,480 kilometers), and in August 2015 will begin a two-month phase known as the high-altitude mapping orbit.

During this phase, the spacecraft will continue to acquire near-global maps with the VIR and framing camera at higher resolution than in the survey phase.

The spacecraft will also image in "stereo" to resolve the surface in 3-D.

NASA DAWN View of Asteroid Vesta

As NASA's Dawn spacecraft travels to its next destination, this mosaic synthesizes some of the best views the spacecraft had of the giant asteroid Vesta. 

Dawn studied Vesta from July 2011 to September 2012. 

The towering mountain at the south pole - more than twice the height of Mount Everest - is visible at the bottom of the image. 

The set of three craters known as the "snowman" can be seen at the top left.

These images are the last in Dawn's Image of the Day series during the cruise to Dawn's second destination, Ceres. A full set of Dawn data is being archived at http://pds.nasa.gov/ .

Read more: Dawn Reality-Checks Telescope Studies of Asteroids

Image credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA

NASA Dawn Vesta: Satellite detects Hydrated Minerals on Giant Asteroid

This map from NASA's Dawn mission shows the global distribution of hydrogen on the surface of the giant asteroid Vesta. 
Credit: NASA JPL-Caltech UCLA PSI MPS DLR IDA.

NASA's Dawn spacecraft has revealed that the giant asteroid Vesta has its own version of ring around the collar.

Two new papers based on observations from the low-altitude mapping orbit of the Dawn mission show that volatile, or easily evaporated materials, have colored Vesta's surface in a broad swath around its equator.

Pothole-like features mark some of the asteroid's surface where the volatiles, likely water, released from hydrated minerals boiled off.

While Dawn did not find actual water ice at Vesta, there are signs of hydrated minerals delivered by meteorites and dust evident in the giant asteroid's chemistry and geology. The findings appear in the journal Science.

One paper, led by Thomas Prettyman, the lead scientist for Dawn's gamma ray and neutron detector (GRaND) at the Planetary Science Institute in Tucson, Ariz., describes how the instrument found signatures of hydrogen, likely in the form of hydroxyl or water bound to minerals in Vesta's surface.

"The source of the hydrogen within Vesta's surface appears to be hydrated minerals delivered by carbon-rich space rocks that collided with Vesta at speeds slow enough to preserve their volatile content," said Prettyman.

A complementary paper, led by Brett Denevi, a Dawn participating scientist based at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., describes the presence of pitted terrain created by the release of the volatiles.

Vesta is the second most massive member of the main asteroid belt. The orbit at which these data were obtained averaged about 130 miles (210 kilometers) above the surface.

Dawn left Vesta earlier this month, on Sept. 4 PDT (Sept. 5 EDT), and is now on its way to its second target, the dwarf planet Ceres.

Scientists thought it might be possible for water ice to survive near the surface around the giant asteroid's poles.

Unlike Earth's moon, however, Vesta has no permanently shadowed polar regions where ice might survive.

The strongest signature for hydrogen in the latest data came from regions near the equator, where water ice is not stable.

In some cases, other space rocks crashed into these deposits later at high speed. The heat from the collisions converted the hydrogen bound to the minerals into water, which evaporated.

The holes that were left as the water escaped stretch as much as 0.6 miles (1 kilometer) across and go down as deep as 700 feet (200 meters). Seen in images from Dawn's framing camera, this pitted terrain is best preserved in sections of Marcia crater.

"The pits look just like features seen on Mars, but while water was common on Mars, it was totally unexpected on Vesta in these high abundances," said Denevi.

"These results provide evidence that not only were hydrated materials present, but they played an important role in shaping the asteroid's geology and the surface we see today."

NASA's Dawn spacecraft Leaves Vesta and sets sail for Ceres

After becoming the first spacecraft to enter orbit around an object in the main asteroid belt between Mars and Jupiter in July 2011, NASA’s Dawn spacecraft has spent the last year mapping the giant asteroid Vesta.

The spacecraft has now bid adieu to Vesta, one of the largest asteroids in the Universe and is on its way to the dwarf planet Ceres to continue its mission to help shed light on the evolution of our solar system.

Communications sent via NASA’s Deep Space Network confirmed Dawn’s departure from Vesta at about 11:26 p.m. US PDT on Tuesday, September 4.

Launched on September 27, 2007, it took the spacecraft almost four years to reach its first port of call, but the second leg of its journey is set to be a bit quicker with Dawn expected to arrive at Ceres early in 2015.

Dawn’s departure from Vesta was far from dramatic.

It gently spiraled out of the giant asteroid's orbit propelled by, what Marc Rayman, Dawn's chief engineer and mission director, called “a blue-green pillar of xenon ions,” emitted from the ion propulsion system that generates thrust by using electricity to ionize xenon.

NASA Dawn: Probe Departing Asteroid Vesta for Ceres

This image taken by the NASA Dawn spacecraft shows the south pole of the giant asteroid Vesta. 

After spending a year examining Vesta, Dawn is poised to depart and head to another asteroid, Ceres, where it will arrive in 2015.

Picture: NASA/AP

NASA Dawn Asteroid Probe Hits Snag on Way to Dwarf Planet, Ceres

An artist's impression of the Dawn spacecraft in orbit around Vesta.

CREDIT: NASA/JPL-Caltech

A NASA spacecraft orbiting the huge asteroid Vesta has suffered a glitch last week, but mission controllers say it will not affect plans for its upcoming trip to Ceres, the largest asteroid or Dwarf Planet, in the solar system.

The malfunction on NASA's Dawn spacecraft occurred during a maneuver on Aug. 8, when one of the probe's reaction wheels that is used to maintain its position in space unexpectedly shut down.

Mission controllers discovered the problem during a routine communications dispatch the following day, on Aug. 9, said Marc Rayman, chief engineer and mission director of the Dawn mission.

"The wheel was operating normally, and then the internal friction increased enough that the software that we call 'fault protection' — it's a system software that looks at parameters on the spacecraft and monitors the performance of the different components — detected something unusual," Rayman reported.

"If something isn't within the limits we've specified, it takes action. In this case, when the friction got up to a certain level, it turned that wheel off."

Three impact craters of different sizes, arranged in the shape of a snowman, make up one of the most striking features on Vesta, as seen in this view from NASA’s Dawn mission. 

In this view the three “snowballs” are upside down, so that the shadows make the features easily recognizable. 

North is to the lower right in the image, which has a resolution of 230 feet (70 meters) per pixel. 

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

At the time when one of the probe's reaction wheels failed, Dawn was preparing for its departure from Vesta, after spending more than a year studying the asteroid.

The spacecraft completed its science objectives at Vesta on July 24. Since then, Dawn has been using its ion thrusters to gradually spiral away from the space rock.

"The ion propulsion system, while very efficient, is also very gentle," Rayman explained.

"It only gradually climbs away from Vesta, spiraling in ever larger loops until the spacecraft is going fast enough and is far away enough from Vesta that Vesta can no longer hold it in its gravitational grip."

Dawn Spacecraft Beams Back New Photo

NASA's Dawn spacecraft obtained this image with its framing camera on July 18, 2011. It was taken from a distance of about 6,500 miles (10,500 kilometers) away from the protoplanet Vesta. The smallest detail visible is about 1.2 miles (2.0 km). Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Dawn took this image during its current orbit of Vesta, traveling from the day side to the night side.

The large structure near the south pole that showed up so prominently in previous images is visible in the center of the illuminated surface.

Compared to other images, this one shows more of the surface beneath the spacecraft in the shadow of night.
Vesta turns on its axis once every five hours and 20 minutes.

Dawn entered orbit around Vesta on July 15, 2011, and will spend a year orbiting the body.

After that, the next stop on its itinerary will be an encounter with the dwarf planet Ceres.

When minor planets Ceres and Vesta rock the Earth into chaos

Astronomy and Astrophysics is publishing a new study of the orbital evolution of minor planets Ceres and Vesta, a few days before the flyby of Vesta by the Dawn spacecraft.

A team of astronomers found that close encounters among these bodies lead to strong chaotic behavior of their orbits, as well as of the Earth's eccentricity.

This means, in particular, that the Earth's past orbit cannot be reconstructed beyond 60 million years.

Astronomy and Astrophysics is publishing numerical simulations of the long-term evolution of the orbits of minor planets Ceres and Vesta, which are the largest bodies in the asteroid belt, between Mars and Jupiter.

Ceres is 6000 times less massive than the Earth and almost 80 times less massive than our Moon. Vesta is almost four times less massive than Ceres.

These two minor bodies, long thought to peacefully orbit in the asteroid belt, are found to affect their large neighbors and, in particular, the Earth in a way that had not been anticipated. This is showed in the new astronomical computations released by Jacques Laskar from Paris Observatory and his colleagues.

Although small, Ceres and Vesta gravitationally interact together and with the other planets of the Solar System. Because of these interactions, they are continuously pulled or pushed slightly out of their initial orbit.

Calculations show that, after some time, these effects do not average out. Consequently, the bodies leave their initial orbits and, more importantly, their orbits are chaotic, meaning that we cannot predict their positions.

The two bodies also have a significant probability of impacting each other, estimated at 0.2% per billion year. Last but not least, Ceres and Vesta gravitationally interact with the Earth, whose orbit also becomes unpredictable after only 60 million years.

This means that the Earth's eccentricity, which affects the large climatic variations on its surface, cannot be traced back more than 60 million years ago. This is indeed bad news for Paleoclimate studies.

This unexpected discovery comes at a time when both objects are the targets of the NASA/Dawn mission. The Dawn probe will encounter Ceres in February 2015. At present, Dawn is approaching Vesta, and the flyby will occur on this coming Saturday, July 16, 2011.