Artist's conception of the NASA Dawn spacecraft approaching Ceres. Credit: NASA
NASA’s Dawn spacecraft experienced technical problems in the past week that will force it to arrive at dwarf planet Ceres one month later than planned, the agency said in a statement yesterday (Sept. 16).
Controllers discovered Dawn was in safe mode Sept. 11 after radiation disabled its ion engine, which uses electrical fields to “push” the spacecraft along. The radiation stopped all engine thrusting activities. The thrusting resumed Monday (Sept. 15) after controllers identified and fixed the problem, but then they found another anomaly troubling the spacecraft.
Dawn’s main antenna was also disabled, forcing the spacecraft to send signals to Earth (a 53-minute roundtrip by light speed) through a weaker secondary antenna and slowing communications. The cause of this problem hasn’t been figured out yet, but controllers suspect radiation affected the computer’s software. A computer reset has solved the issue, NASA added. The spacecraft is now functioning normally.
Vesta (left) and Ceres. Vesta was photographed up close by the Dawn spacecraft from July 2011-Sept. 2012, while the best views we have to date of Ceres come from the Hubble Space Telescope. The bright white spot is still a mystery. Credit: NASA
“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. The plans for exploring Ceres once the spacecraft is in orbit, however, are not affected,” NASA’s Jet Propulsion Laboratory stated in a press release.
Dawn is en route to Ceres after orbiting the huge asteroid Vesta between July 2011 and September 2012. A similar suspected radiation blast three years ago also disabled Dawn’s engine before it reached Vesta, but the ion system worked perfectly in moving Dawn away from Vesta when that phase of its mission was complete, NASA noted.
Among Dawn’s findings at Vesta is that the asteroid is full of hydrogen, and it contains the hydrated mineral hydroxyl. This likely came to the asteroid when smaller space rocks brought the volatiles to its surface through low-speed collisions.
Spacecraft can experience radiation through energy from the Sun (particularly from solar flares) and also from cosmic rays, which are electrically charged particles that originate outside the Solar System. Earth’s atmosphere shields the surface from most space-based radiation.
The Meteorite of Serooskerken (Source: Sterrenwacht Sonnenborgh)
Here’s a bit of good news: the Serooskerken meteorite, which was stolen from the Sonnenborgh Museum and Observatory in Utrecht, Netherlands on Monday night, has been recovered. It was found in a bag left in some bushes alongside a tennis court and turned in to the police.
It’s not quite “game, set, match” though; unfortunately the meteorite was broken during the theft. (See a photo here via Twitter follower Marieke Baan.) Still, the Sonnenborgh Museum director is glad to have the pieces back, which he said will remain useful for research and can still be exhibited. (Source)
The Serooskerken meteorite was recovered from a fall in the Dutch province of Zeeland on August 28, 1925. Classified as a diogenite (HED) it is thought to have originated from the protoplanet Vesta, the second most massive object in the main asteroid belt between the orbits of Mars and Jupiter (and the previous target of NASA’s Dawn mission.) It is one of only five meteorite specimens ever recovered in the Netherlands.
The meteorite was one of several items reported stolen from the Sonnenborgh Museum on the night of August 18-19, 2014.
The Meteorite of Serooskerken (Source: Sterrenwacht Sonnenborgh)
Calling all meteorite collectors and enthusiasts! There’s a hot space rock at large and, as Indiana Jones would say, it belongs in a museum. Perhaps you can help put it back in one.
Mosaic of the asteroid Vesta made from images acquired by NASA’s Dawn spacecraft. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA
On Aug. 19 a burglary was reported at the Sonnenborgh Museum and Observatory in Utrecht, Netherlands, and one of the items missing is a meteorite that is thought to have originated from the asteroid Vesta.
Seen above in a photo from the museum’s collection, the Meteorite of Serooskerken was recovered from a rare fall in 1925 in the province of Zeeland. Only five meteorites have ever been found in the Netherlands, making the Serooskerken specimen somewhat of a national treasure – not to mention a valuable piece of our Solar System’s history!
About 5–6% of all the meteorites found on Earth are thought to be from Vesta, the second-largest world in the main asteroid belt. (Source)
It doesn’t sound like the meteorite was the target of the burglary, but rather it just happened to be included with other things taken from the museum’s safe.
The asteroid Vesta as seen by the Dawn spacecraft. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA
While “dark materials” may leave some of us thinking about a certain Philip Pullman book series, on the asteroid Vesta its presence belies something equally exotic: old smaller asteroid impacts on its surface.
The dark stuff on the lighter surface has puzzled researchers since it was discovered in 2011 (and has been brought up in other studies), but a new team says it has found that serpentine is among the components. Because that mineral can’t survive temperatures that are more than 400 degrees Celsius (752 degrees Fahrenheit), this means that scenarios such as volcanic eruptions can’t have caused it. This leaves only smaller asteroids, the team says.
“These meteorites are regarded as fragments of carbon-rich asteroids. The impacts must have been comparatively slow, because an asteroid crashing at high speeds would have produced temperatures too high to sustain serpentine,” the Max Planck Institute for Solar System Research stated.
Image of the crater Numisia on Vesta, where researchers found the spectral signature of serpentine. Picture taken by NASA’s Dawn spacecraft. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
“In a previous study, scientists from the MPS had calculated how dark material would be distributed on Vesta as a result of a low-speed oblique impact. Their results are consistent with the distribution of dark material on the edge of one of the two large impact basins in the southern hemisphere.”
The results came from analyzing images the NASA Dawn spacecraft took of Vesta between July 2011 and September 2012. The researchers recalibrated the data and also backed up their results by examining serpentine in laboratory conditions.
Ceres and Vesta are converging in Virgo not far from Mars and Spica. On July 5, the duo will be just 10' apart and visible in the high power telescope field of view. Positions are shown every 5 days for 10 p.m. EDT and stars to magnitude +8.5. Created with Chris Marriott's SkyMap software
I bet you’ve forgotten. I almost did. In April, we reported that Ceres and Vesta, the largest and brightest asteroids respectively, were speeding through Virgo in tandem. Since then both have faded, but the best is yet to come. Converging closer by the day, on July 5, the two will make rare close pass of each other when they’ll be separated by just 10 minutes of arc or the thickness of a fat crescent moon.
Vesta (left) and Ceres. Vesta was photographed up close by the Dawn spacecraft from July 2011-Sept. 2012, while the best views we have to date of Ceres come from the Hubble Space Telescope. The bright white spot is still a mystery. NASA will plunk Dawn into orbit around Ceres next February. Credit: NASA
Both asteroids are still within range of ordinary 35mm and larger binoculars; Vesta is easy at magnitude +7 while Ceres still manages a respectable +8.3. From an outer suburban or rural site, you can watch them draw together in the coming two weeks as if on a collision course. They won’t crash anytime soon. We merely see the two bodies along the same line of sight. Vesta’s closer to Earth at 164 million miles (264 million km) and moves more quickly across the sky compared to Ceres, which orbits 51 million miles (82 million km) farther out.
Ceres and Vesta lie near an easy naked eye star, Zeta Virginis, which forms an isosceles triangle right now with Mars and Spica. The map shows the sky around 10 p.m. local time tonight facing southwest. Stellarium
Right now the two asteroids are little more than a moon diameter apart not far from the 3rd magnitude star Zeta Virginis. Happily, nearby Mars and Spica make excellent guides for finding Zeta. Once you’re there, use binoculars and the more detailed map to track down Ceres and Vesta.
Virgo will be busy Saturday night July 5, 2014 when the waxing moon passes about 1/2 degree from Mars as Ceres and Vesta squeeze closest. Stellarium
In early July they’ll look like a wide double star in binoculars and easily fit in the same high power telescopic view. Vesta has always looked pale yellow to my eye. Will its color differ from Ceres? Sitting side by side it will be easier than ever to compare them. Vesta is a stony asteroid with a surface composed of solidified (and meteoroid-battered) lavas; Ceres is darker and covered with a mix of water ice and carbonaceous materials.
On the night of closest approach, it may be difficult to spot dimmer Ceres in binoculars. By coincidence, the 8-day-old moon will be very close to the planet Mars and brighten up the neighborhood. We’ll report more on that event in a future article.
With so much happening the evening of July 5, let’s hope for a good round of clear skies.
This map shows the paths of Ceres and Vesta in Virgo through late June at five-day intervals. Vesta is currently magnitude +5.8 and Ceres 7.0. Both are easily visible in binoculars from suburban and rural skies. A wide view map below will help you navigate from nearby bright Mars to Zeta Virginis. From Zeta, star hop to either asteroid. Stars are shown to about magnitude +8.5. Click to enlarge. Created with Chris Marriott's SkyMap software
Don’t let them pass you by. Right now and continuing through July, the biggest and brightest asteroids will be running on nearly parallel tracks in the constellation Virgo and so close together they’ll easily fit in the same binocular field of view. The twofer features Ceres (biggest) and Vesta (brightest) which are also the prime targets of NASA’s Dawn Mission. Now en route to a Ceres rendezvous next February, Dawn orbited Vesta from July 2011 to September 2012 and sent back spectacular photos of two vast impact basins, craters stained black by carbon-rich asteroids and parallel troughs that stretch around the 330-mile-wide world like rubber bands.
This mosaic of Vesta synthesizes some of the best views the spacecraft had of the giant asteroid. 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. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA
Astronomers used Dawn’s gravity data to discover Vesta is more like a planet than anyone had supposed. Deep beneath its crust, composed of lighter minerals, lies a denser iron core. Most asteroids were too small to generate enough interior heat through the decay of radioactive elements to melt and “differentiate” into core, mantle and crust like the terrestrial planets. Thanks to our new understanding, you’ll hear Vesta referred to as a ‘baby planet’.
A full 5.3 hour rotation of Vesta using photos taken by Dawn. Credit: NASA
Studies of its crustal rocks showed a match to a clan of basaltic meteorites called howardites, eucrites and diogenites. Many of these formerly volcanic rocks that trace their origin to Vesta are found in numerous private and institutional collections. With a little homework, you can even buy a slice of Vesta on eBay, making for one of the least expensive sample return missions ever undertaken.
Dawn’s Greatest Hits at Vesta – A quick summary of key discoveries accompanied by electric guitar
While Vesta is a rocky body, Ceres shows telltale signs of water and iron-rich clay. Like Vesta, it also appears to have cooked itself into denser core and lighter crust. Because Ceres is less dense than Earth, astronomers believe water ice may be buried beneath its dusty crust.
Dwarf planet Ceres (right) is located in the asteroid belt, between the orbits of Mars and Jupiter. Observations by ESA’s Herschel space observatory between 2011 and 2013 found that the dwarf planet has a thin water-vapor atmosphere. It’s the first unambiguous detection of water vapor around an object in the asteroid belt. Credit: ESA/ATG medialab
Earlier this year, astronomers working with the Herschel Space Telescope announced the discovery of plumes of water vapor blasting from two regions on the dwarf planet’s surface. While Ceres is an asteroid it’s also a member of a select group of dwarf planets, bodies large enough to have crunched themselves into spheres through their own gravity but not big enough to clear the region they orbit of smaller asteroids.
Vesta (left) and Ceres. Vesta was photographed up close by Dawn, while the best views we have to date of Ceres come from the Hubble Space Telescope. Notice the bright white spot which is still a mystery. Credit: NASA/ESA
Ceres and Vesta will be gradually drawing closer in the coming weeks and months until on July 5 only 10 arc minutes (one-third the diameter of a full moon) will separate them. They’ll also be fading, but not so much that binoculars won’t show them throughout this excellent dual apparition. Vesta will only dim to magnitude +7 by July 1, Ceres to 8.4. Come mid-June I’ll return with a detailed map showing how best to see the dynamic duo during their close conjunction.
To find your way to the 4th magnitude stars Zeta and Tau Virginis, which you can use with the detailed map to guide you to Ceres and Vesta, start with brilliant Mars in the southern sky and look about one fist to the left or east to spot Zeta. Map shows the sky around 10 o’clock local time in late April. Stellarium
Sure, both Ceres and Vesta look exactly like stars even in large amateur telescopes, but sampling photons from real asteroids while listening to the sound of frogs on a spring night is my idea of a good time. Maybe yours too. Good luck!
Artist's conception of the Dawn spacecraft approaching the asteroid Ceres. Credit: NASA/JPL-Caltech
The next few years will be banner ones for learning about dwarf planets. While the high-profile New Horizons spacecraft zooms towards a Pluto date in 2015, the Dawn spacecraft is making a more stealthy (in terms of media coverage) run at Ceres, which is the smallest and closest dwarf planet to Earth.
The Dawn spacecraft, as readers likely recall, made its first port of call at fellow protoplanet Vesta. What excites scientists this time around is the likelihood of water ice on Ceres’ surface. Vesta, by contrast, was very dry.
Here’s Dawn’s agenda once it gets to Ceres in April 2015:
“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),” NASA stated.
“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.”
Dawn will then zoom down to an altitude of just 233 miles (375 kilometers) in November 2015 for three months to obtain information about elements and the dwarf planet’s gravity. Dawn will use its Gamma Ray and Neutron Detector (GRaND) to do the first part and a gravity experiment to perform the second.
Ceres. Image credit: NASA
To conserve fuel, Dawn will also use a “hybrid” pointing control method to keep it on track, using both reaction wheels and thrusters to stay in the right direction. This is needed because two of its four reaction wheels had “developed excessive friction” by the time Dawn departed Vesta. The hybrid method was tested for 27 hours and successfully concluded Nov. 13. You can check out more about the hybrid mode at this link.
The mineral olivine on Vesta, as seen from hyperspectral data received during the Dawn mission. Credit: Image generated by Alessandro Frigeri and Eleonora Ammannito using VIR data and Framing Camera images.
That ghoul-like sheen on the asteroid Vesta, as seen in the image above, is not some leftover of Hallowe’en. It’s evidence of the mineral olivine. Scientists have seen it before in “differentiated” bodies — those that have a crust and an inner core — but in this case, it’s turning up in an unexpected location.
Finding olivine is not that much of a surprise. Vesta is differentiated and also (likely) is the origin point of diogenite meteorites, which are sometimes olivine-rich. Researchers expected that the olivine would be close to the diogenite rocks, which in Vesta’s case are in areas of the south pole carved out from the mantle.
NASA’s Dawn mission to the asteroid did a search in areas around the south pole — “which are thought to be excavated mantle rocks”, the researchers wrote — but instead found olivine in minerals close to the surface in the northern hemisphere. These minerals are called howardites and are normally not associated with olivine. So what is going on?
Artist’s conception of the Dawn mission. Credit: NASA
Basically, it means that Vesta’s history was far more complex than we expected. This situation likely arose from a series of impacts that changed around the eucritic (stony meteorite) crust of Vesta:
“A generalized geologic history for these olivine-rich materials could be as follows: ancient large impacts excavated and incorporated large blocks of diogenite-rich and olivine-rich material into the eucritic crust, and subsequent impacts exposed this olivine-rich material,” the researchers wrote.
“This produced olivine-rich terrains in a howarditic background, with diogene-rich howardites filling nearby, eroded, older basins.”
Dawn, by the way, has completed its time at Vesta and is now en route to another large asteroid, Ceres. But there’s still plenty of data for analysis. This particular research paper was led by E. Ammannito from the Institute of Astrophysics and Space Planetology (Istituto di Astrofisica e Planetologia Spaziali) in Rome. The research appears in this week’s Nature and should be available shortly at this link.
An atlas of the asteroid, Vesta, created from mosaics of 10 000 images from Dawn’s framing camera (FC) instrument, taken during the Dawn Mission’s Low Altitude Mapping Orbit (LAMO) an altitude of around 135 miles (210 kilometres). Credit: European Space Agency
Now’s your big chance to get up close and personal with Vesta, one of the largest asteroids in the solar system.
A new atlas has been released based on 10,000 images from the Dawn mission‘s framing camera instrument, which took the pictures from an average altitude of about 131 miles (210 kilometers). Each map has a scale of 1 centimetre to 2 kilometres (roughly a scale of 0.4 inches : 1.2 miles).
“Creating the atlas has been a painstaking task – each map sheet of this series has used about 400 images,” stated Thomas Roatsch, who is with the German Aerospace Center (DLR) Institute of Planetary Research and led the work.
This image from NASA’s Dawn spacecraft shows a close up of part of the rim around the crater Canuleia on the giant asteroid Vesta. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/PSI/Brown
“The atlas shows how extreme the terrain is on such a small body as Vesta. In the south pole projection alone, the Severina crater contours reaches a depth of 18 kilometres [11 miles]; just over 100 kilometres [62 miles] away the mountain peak towers 7 kilometres [4.3 miles] above the … reference level.”
An impact structure on asteroid Vesta resembling a snowman. Credit: NASA
When Heinrich Wilhelm Olbers first glimpsed Vesta on March 29, 1807 — this date in history — the asteroid was but a small point of light. Asteroid science was very, very new at the time as the first asteroid (Ceres) had been discovered only six years before.
Fast-forward 200-plus years and we can treat Vesta as a little world in its own right. NASA sent the Dawn spacecraft in orbit for about a year, which has produced a wealth of weird results. (Stay tuned for what happens at Dawn’s next port of call: Ceres.)
Below are five strange things we’ve discovered about Vesta:
1) Vesta has a fresh face.
This image from NASA’s Dawn spacecraft shows a close up of part of the rim around the crater Canuleia on the giant asteroid Vesta. Canuleia, about 6 miles (10 kilometers) in diameter, is the large crater at the bottom-left of this image. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/PSI/Brown
Space “weathering” from tiny particles hitting the Moon has shaped the surface over time. Not so much on Vesta. It turns out the topography on the asteroid (and other factors) allow constant mixing of the surface, making it appear almost new even though the asteroid is several billion years old. “Vesta ‘dirt’ is very clean, well mixed and highly mobile,” said Carle Pieters, one of the lead authors and a Dawn team member based at Brown University, Providence, R.I. when the finding was made public.
2) Vesta might have stretch marks.
Dawn image of Vesta showing its nearly circumferential equatorial grooves (NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)
While trying to wrap their mind around fault lines that circle Vesta’s equator, a group of scientists proposed these could be graban — features that show surface expansion. It’s possible these faults came to be after something big smashed into the planet, creating a gigantic crater with a peak that is almost three times as high as Mt. Everest. The expansion occurred as Vesta’s interior differentiated, or experienced a separation of its core, mantle and crust.
3) Vesta kind of looks like a planet.
‘Rainbow-Colored Palette’ of Southern Hemisphere of Asteroid Vesta from NASA Dawn Orbiter. This mosaic using color data obtained by the framing camera aboard NASA’s Dawn spacecraft shows Vesta’s southern hemisphere in false color, centered on the Rheasilvia impact basin, about 290 miles (467 kilometers) in diameter with a central mound reaching about 14 miles (23 kilometers) high. The black hole in the middle is data that have been omitted due to the angle between the sun, Vesta and the spacecraft. The green areas suggest the presence of the iron-rich mineral pyroxene or large-sized particles. This mosaic was assembled using images obtained during Dawn’s approach to Vesta, at a resolution of 480 meters per pixel. The German Aerospace Center and the Max Planck Institute for Solar System Research provided the Framing Camera instrument and funding as international partners on the mission team. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Looking at Vesta in false color — wavelengths that let different kinds of minerals shine — show a veritable cornucopia of different types of stuff. There’s the iron-rich mineral pyroxene, there’s diagenite material (characteristic of stony meteorites), and various particles of different sizes and ages. “Vesta is a transitional body between a small asteroid and a planet and is unique in many ways,” said mission scientist Vishnu Reddy of the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany. “We do not know why Vesta is so special.”
4) Vesta has hydrogen.
Hydrated minerals are circling the equator of the little world. It’s not quite water, but still an interesting find for scientists. “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,” stated Thomas Prettyman, lead scientist for Dawn’s gamma ray and neutron detector (GRaND) from the Planetary Science Institute.
5) The northern and southern hemispheres look completely different.
Shaded-relief topographic map of Vesta southern hemisphere showing two large impact basins – Rheasilvia and Older Basin. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
It’s fun to get to a new world and end up with something fundamentally surprising. Some of the very first pictures of Vesta showed a vast difference between different regions of the planet, giving scientists a workout in terms of figuring out how that came to be. “The northern hemisphere is older and heavily cratered in contrast to the brighter southern hemisphere where the texture is more smooth and there are lots of sets of grooves. There is a massive mountain at the South Pole. One of the more surprising aspects is the set of deep equatorial troughs,” said Carol Raymond, Dawn deputy principal investigator, of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
Here’s a video where you can see that for yourself:
