A radar image an asteroid, 2005 YU55, acquired in April 2010. (This is not the asteroid that will pass by Earth on Jan. 27, 2012)Credit: NASA
NASA’s Jet Propulsion Laboratory released this video today featuring more information about the much-discussed 2005 YU55, a 400-meter-wide asteroid that will pass by Earth next Tuesday at a distance closer than the Moon. The video features research scientist Lance Benner, an expert in radio imaging of near-Earth objects.
While YU55 will come closer than any object we’ve been aware of in the past 35 years, it poses no risk to Earth.
“2005 YU55 cannot hit Earth, at least over the interval that we can compute the motion reliably, which extends for several hundred years.”
– Lance Benner, JPL Research Scientist
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While we can’t state enough that there’s no danger from YU55, this close pass will offer a fantastic opportunity for scientists to acquire detailed radar images of this ancient C-type asteroid.
NASA’s Near-Earth Objects Observation Program will continue tracking YU55 using the 70-meter radar telescope at the Deep Space Network in Goldstone, California, as well as with the Arecibo Planetary Radar Facility in Puerto Rico.
“This is the closest approach by an asteroid this large that we’ve known about in advance,” said Benner. “The Goldstone telescope has a new radar imaging capability which has just become available that will enable us to see much finer detail than has previously been possible.”
Radar imaging allows scientists to better study the surface features and composition of fast-moving, dark objects like YU55 which reflect very little visible light.
Space.com has provided a great infographic that shows exactly where this asteroid will pass by Earth. Note that the side view plainly shows that the path of the asteroid is well above the plane of the Earth/Moon orbit.
A radar image an asteroid, 2005 YU55, acquired in April 2010. (This is not the asteroid that will pass by Earth on Jan. 27, 2012)Credit: NASA
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Yes, it’s coming. Yes, it’s big. Yes, it will be even closer than the Moon. And yes… we’re completely safe.
The 400-meter-wide asteroid 2005 YU55 is currently zipping through the inner Solar System at over 13 km (8 miles) a second. On Tuesday, November 8, at 6:28 p.m. EST, it will pass Earth, coming within 325,000 km (202,000 miles). This is indeed within the Moon’s orbit (although YU55’s trajectory puts it a bit above the exact plane of the Earth-Moon alignment.) Still, it is the closest pass by such a large object since 1976… yet, NASA scientists aren’t concerned. Why?
Because its orbit has been well studied, there’s nothing in its way, and frankly there’s simply nothing it will do to affect Earth.
Animation of 2005 YU55's trajectory on Nov. 8. (NASA/JPL) Click to play.
Period.
2005 YU55’s miniscule gravity will not cause earthquakes. It has no magnetic field. It will not strike another object, or the Moon, or the Earth. It will not come into contact with cometary debris, Elenin, a black dwarf, Planet X, or Nibiru. (Not that those last three even exist.) No, YU55 will do exactly what it’s doing right now: passing through the Solar System. It will come, it will go, and hopefully NASA scientists – as well as many amateur astronomers worldwide – will have a chance to get a good look at it as it passes.
Scientists with NASA’s Near-Earth Objects Observation Program will begin tracking YU55 on Friday, November 4 using the 70-meter radar telescope at the Deep Space Network in Goldstone, California , as well as with the Arecibo Planetary Radar Facility in Puerto Rico beginning November 8. These facilities will continue to track it until the 10th.
This close pass will offer a great opportunity to get detailed radar imaging of YU55, an ancient C-type asteroid literally darker than coal. Since these objects can be difficult to observe using visible light, radar mapping can better reveal details about their surface and composition.
To help inform the public about YU55 NASA’s Jet Propulsion Laboratory in Pasadena recently hosted a live Q&A session on Ustream featuring specialists Marina Brozovic, a Goldstone Radar Team scientist, and Don Yeomans, manager of NASA’s Near-Earth Object Program. They fielded questions sent in via chat and Twitter… a recording of the event in its entirety can be seen below:
Undoubtedly there will still be those who continue to spread misinformation about 2005 YU55. After all, they did the same with the now-disintegrated comet Elenin. But the truth is out there… and the truth is that there’s no danger, no cover-ups, no “plots”, and simply no cause for concern.
UPDATE: JPL has released a brief video about YU55 featuring research scientist Lance Benner, who specializes in radar imaging of near-Earth objects:
Although classified as a potentially hazardous object, 2005 YU55 poses no threat of an Earth collision over at least the next 100 years. However, this will be the closest approach to date by an object this large that we know about in advance and an event of this type will not happen again until 2028 when asteroid (153814) 2001 WN5 will pass to within 0.6 lunar distances. – Near-Earth Object Program, JPL
3 D view of the rare Phobos–Jupiter conjunction taken on 1 June 2011 by the High Resolution Stereo Camera on Mars Express. Credits: ESA/DLR/FU Berlin (G. Neukum)
Video Caption: Phobos and Jupiter in Conjunction – taken from Mars orbit !
A movie of the 1 June 2011 Phobos–Jupiter conjunction made by combining a sequence of 100 images of the encounter taken by the High Resolution Stereo Camera on ESA’s Mars Express orbiter. Mars Express is searching for safe landing zones on Phobos for Russia’s Phobos-Grunt lander blasting off on November 9. Credits: ESA/DLR/FU Berlin (G. Neukum)
3 D images of Phobos-Jupiter conjuction below Update – Phobos-Grunt launch processing photo below
In just 7 days, Russia’s Phobos-Grunt sample return mission will blast off for Mars on November 9 on a daring mission to grab soil samples from the surface of the miniscule martian moon Phobos and return them back to Earth for analysis to give us breathtaking new insights into the formation and evolution of Mars, Phobos and our Solar System.
So, check out the amazing animation and 3 D stereo images of fish-like Phobos and banded Jupiter snapped by Europe’s Mars Express orbiter to get a bird’s eye feel for the battered terrain, inherent risks and outright beauty that’s in store for the Phobos -Grunt spaceship when it arrives in the Red Planet’s vicinity around October 2012. Whip out your red-cyan 3 D glasses – Now !
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ESA’s Mars Express orbiter (MEX) was tasked to help Russia locate suitable and safe landing sites on Phobos’ pockmarked terrain. MEX was built by ESA, the European Space Agency and has been in Mars orbit since 2003.
To capture this impressive series of rare photos of Jupiter and Phobos in conjunction, Mars Express performed a special maneuver to observe an unusual alignment of Jupiter and Phobos on 1 June 2011.
Mars Express High Resolution Stereo Camera (HRSC) snapped a total of 104 images over 68 seconds when the distance from the spacecraft to Phobos was 11,389 km and the distance to Jupiter was 529 million km.
Phobos- Jupiter Conjunction: before, during and after on 1 June 2011 from Mars Express. Credits: ESA/DLR/FU Berlin (G. Neukum)
Enjoy the exquisite views of the bands of Jupiter and imagine exploring the deep pockets and mysterious grooves on Phobos – which may be a captured asteroid.
The camera was kept fixed on Jupiter, to ensure it remained static as Phobos passed in front and which afforded an improvement in our knowledge of the orbital position of Phobos.
Phobos in 3 D during flyby of 10 March 2010. Image taken from a distance of 278 km. Russia’s Phobos-Grunt will retrieve rogolith and rock for return to Earth. Credit: ESA/DLR/FU Berlin (G. Neukum)
NASA’s twin Mars rovers Spirit and Opportunity have also occasionally photographed both of Mars’ moons to further refine their orbital parameters.
NASA’s Curiosity rover remains on track to liftoff for Mars on Nov. 25
Orbital Paths of Phobos and Mars Express. The trajectories of Phobos and Mars Express at the time of the conjunction with Jupiter on 1 June 2011. The letter ‘S’ denotes the South Pole of Mars.Technicians at Baikonur Cosmodrome prepare Phobos-Grunt for upper stage attachment. Credit: Roscosmos
Light echo of dust illuminated by nearby star V838 Monocerotis as it became 600,000 times more luminous than our Sun in January 2002. Credit: NASA/ESA
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Some supermassive black holes are obscured by oddly shaped dust clouds which resemble doughnuts. These clouds have been an unsolved puzzle, but last week a scientist at the University of Leicester proposed a new theory to explain the origins of these clouds, saying that they could be the results of high-speed collisions between planets and asteroids in the central region of galaxies, where the supermassive black holes reside.
While black holes are a death knell for any objects wandering too close, this may mean even planets in a region nearby a black hole are doomed — but not because they would be sucked in. The central regions of galaxies just may be mayhem for planets.
“Too bad for life on these planets, ” said Dr. Sergei Nayakshin, whose paper will be published in the Monthly Notices of the Royal Astronomical Society journal.
In the center of nearly all galaxies are supermassive black holes. Previous studies show that about half of supermassive black holes are obscured by dust clouds.
Nayakshin and his team found inspiration for their new theory from our Solar System, and based their theory on the zodiacal dust which is known to originate from collisions between solid bodies such as asteroids and comets.
The central point of Nayakshin’s theory is that not only are black holes present in the central region of a galaxy, but stars, planets and asteroids as well.
The team’s theory asserts that any collisions between planets and asteroids in the central region of a galaxy would occur at speeds of up to 1000 km/sec. Given the tremendous speeds and energy present in such collisions, eventually rocky objects would be pulverized into microscopic dust grains.
Nayakshin also mentioned that the central region of a galaxy is an extremely harsh environment, given high amounts of deadly radiation and frequent collisions, both of which would make any planets near a supermassive black hole inhospitable well before they were destroyed in any collisions.
While Nayakshin said the frequent collisions would be bad news for any life that may exist on the planets, he added, “On the other hand the dust created in this way blocks much of the harmful radiation from reaching the rest of the host galaxy. This in turn may make it easier for life to prosper elsewhere in the rest of the central region of the galaxy.”
Nayakshin believes that a greater understanding of the origins of the dust near black holes is important to better understand how black holes grow and affect their host galaxy, and concluded with, “We suspect that the supermassive black hole in our own Galaxy, the Milky Way, expelled most of the gas that would otherwise turn into more stars and planets. Understanding the origin of the dust in the inner regions of galaxies would take us one step closer to solving the mystery of the supermassive black holes.”
Almahata Sitta 15. The black fragment of Almahata Sitta meteorite number 15 shows up black against the lighter coloured rocks of the Nubian desert in Northern Sudan. Image credit: Peter Jenniskens (SETI Institute/NASA Ames)
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It was an unprecedented event: On October 6, 2008, asteroid 2008 TC3 was spotted by the Catalina Sky Survey Telescope in Arizona. Plotting its trajectory, astronomers knew the 80-ton rock was heading for a collision course with Earth. Just 19 hours later, 2008 TC3 streaked over skies of northern Sudan and then exploded about 37 km above the Nubian Desert. This was the first time an asteroid was predicted – and predicted correctly — to impact Earth. Luckily, it wasn’t big enough to cause any problems, and its path brought it over a remote area. But this presented scientists with an exciting and unparalleled opportunity to possibly study fragments of an asteroid that had been spectrally classified before striking Earth.
Shortly afterwards, expeditions led by Dr. Peter Jenniskens, a meteor astronomer from SETI and NASA’s Ames Research Center, and Mauwia Shaddad, a physicist at the University of Khartoum, collected nearly 600 pieces of the asteroid strewn over 29 kilometers of desert. Altogether the meteorites weighed less than 10 kilograms – all that was left of the 80-ton asteroid.
But these fragments that fell to Earth are revealing secrets about the asteroid belt and the early days of the solar system, says Dr. Jon Friedrich from Fordham University, one of the many different researchers who have been studying pieces of the fragments, now called the “Almahata Sitta” meteorites.
“We can now say the asteroid belt has lots of different types of materials that give little snapshots of conditions within the early solar system,” Friedrich told Universe Today. “We’ve seen that these asteroids haven’t changed a whole lot since the Solar System formed, so it speaks to the diversity of the chemistry and the processes that were acting on these small bodies in the early Solar System.”
Scientists agree that understanding the composition of the asteroid belt is crucial to how we might deal with a larger asteroid that might be heading directly towards Earth.
Discovery images of asteroid 2008 TC3, as it was seen on October 6, 2008, by the Catalina Sky Survey at Mount Lemmon in Arizona (Richard Kowalski).
Although scientists have been able to study and catalog many thousands of meteorites and have also analyzed hundreds of asteroids in space, this is the first time a “fresh” chunk of an asteroid that has fallen to Earth as a meteorite — and been analyzed through spectroscopy while it was still in space — has been found so quickly after hitting Earth. These meteorites are the first to be unequivocally connected with its parent asteroid.
“It is amazing to be able to finally positively link an asteroid to a certain type of meteorite,” said Friedrich. “When we look at asteroids in space we are only looking at the outside, and the asteroid’s surface has changed from being in the environment of space. For the first time we can study the interior of an object we have seen the exterior of in space. That knowledge gives us a map as to how the exteriors of asteroids change. We can have a better understanding of the population of objects in space and their distribution in the solar system.”
About three-quarters of meteorites that are found on Earth are an “ordinary” kind of stony meteorites called chondrites. Analysis of the Almahata Sitta meteorites revealed a rare, carbon-rich type of meteorite called an ureilite. Ureilites are believed to come from a large organic–rich, primitive asteroid that had melted sometime in its past.
“These are a strange type of meteorite which are rather odd in the sense that it is an igneous rock, much like a volcanic rock here on Earth,” Friedrich said, “so this meteorite’s origin is from a magma, so they were surely melted at one point. That also means they are like rocks you might pick up on Earth, but they also contain what we might call relatively primitive materials also, like graphite, organic compounds and other things.”
And so ureilites, and in particular the Almahata Sitta meteorites, contain material from both primitive and evolved types of asteroids.
There are few ureilites in meteorite collections, which is another reason the Almahata Sitta meteorites are so interesting. They have an unusually fine-grained and porous texture, making the meteorites extremely fragile. The researchers think that is why Asteroid 2008 TC3 shattered high in Earth’s atmosphere.
Friedrich and a student at Fordham, Julianna Troiano, studied fragments of the meteorites using an inductively coupled plasma mass spectrometer, which specializes in looking at inorganic composition of rock.
“We found chemically that all the different pieces were indeed ureilites,” Friedrich said, “but one other interesting thing was that these don’t seem to have any evidence of terrestrial contamination at all, which is what you would expect from such a ‘fresh’ fall. Most ureilite meteorites have been found in Antarctica, and oftentimes, the Antarctic samples seem to have concentrations that are somewhat elevated in certain elements, such are rare Earth elements like lanthanum, cerium. But the Almahata Sitta meteorites don’t seem to have an obvious contamination signature.”
Various meteorites from 2008 TC3. Credit: P. Jenniskens, et. al. Click image for full description
This allows the researchers to better explore the solar system’s makeup.
While chondrites normally have not been modified due to melting or differentiation of the parent asteroid — and researchers suspect they are not necessarily representative of typical asteroid parent bodies — ureilites normally do show signs of the parent body being melted.
So what has happened to an asteroid that is has somehow been heated to the point of “melting?”
The latest research on the Almahata Sitta meteorites reveal that the parent asteroid was probably formed through collisions of three different types of asteroids. This would also explain why the meteorites contain both evolved and primitive asteroid materials.
Dr. Julie Gayon-Markt from the Observatoire de la Cote d’Azur in France also recently provided more insight on the family of asteroids from which 2008 TC3 originated.
“Because falls of meteorites of different types are rare, the question of the origin of an asteroid harbouring both primitive and evolved characteristics is a challenging and intriguing problem,” said Gayon-Markt, who presented her findings at the Europlanet Science Conference in October. “A workable explanation for how asteroid 2008TC3 could have formed involves low velocity collisions between these asteroid fragments of very different mineralogies.
Gayon-Markt and her team also looked at the dynamics and spectroscopy of asteroids in the main asteroid belt to shed light on the origin of the Almahata Sitta fragments. “We show that the Nysa-Polana asteroid family, located in the inner Main Belt is a very good candidate for the origin of 2008 TC3,” she said.
Primitive asteroids, which are relatively unchanged since the birth of the Solar System, contain high proportions of hydrated minerals and organic materials. However, many other asteroids have undergone heating at some point, probably through the decay of radioactive materials, and the molten magma has separated into an iron core surrounded by a rocky mantle.
Friedrich and Gayton-Markt are just two of the researchers who are studying the Almahatta Sitta meteorites to try and garner a better understanding of our solar system, as well as figuring out more about the asteroid that fell to Earth in 2008.
“The study of these meteorites has been interdisciplinary and collaborative, and our work is just a small piece of a greater puzzle,” Friedrich said.
Several images have been combined into a map of the asteroid. This image represents the total area viewed by the spacecraft during the flyby, which amounted to more than 50% of Lutetia’s surface. Credits: ESA 2011 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA
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Way out in space, 282 million miles from home, the intrepid ESA Rosetta spacecraft is still busy, but had time to send us an unprecedented view of ancient asteroid Lutetia. On July 10, 2010, Rosetta flew past Lutetia and the results of the imaging revealed surface features which point to an astonishing history. This particular asteroid might not have a “heart of gold”, but it may very well have – or had – a molten interior.
Buzzing by at a speed of 54 000 km/hr and a closest distance of 3170 km, Rosetta took a series of high resolution images and returned them to an international team of researchers from France, Germany, the Netherlands and the United States. By closely examining the craters, cracks and surface, the team was able to determine that Lutetia survived a multitude of impacts – yet retained much of its original structure.
Benjamin Weiss, an associate professor of planetary sciences in MIT’s Department of Earth, Atmospheric and Planetary Sciences, reports Lutetia may have a molten core and this finding shows a “hidden diversity” for known structures within the greater asteroid belt.
“There might be many bodies that have cores and interesting interiors that we never noticed, because they’re covered by unmelted surfaces,” says Weiss, who is a co-author on both Science papers and lead author for the paper in PSS. “The asteroid belt may be more interesting than it seems on the surface.”
Although the encounter was brief, images from the OSIRIS camera revealed some surface features which are believed to be up to 3.6 billion years old – while others appear to be 50-80 million. These ages can be estimated through impact events and the amount and distribution of ejecta. Some of the areas on Lutetia are heavily cratered, implying greater age, while others appear to be landslide events perhaps caused by nearby fractures. While most asteroids are small, light, and have smooth surfaces – Lutetia is different. It appears to be dense, yet relatively porous… a finding that points toward a “dense metallic core, with a once melted interior underneath its fractured crust.”
“We don’t think Lutetia was born looking like this,” says Holger Sierks, of the Max-Planck-Institut für Sonnensystemforschung, Lindau, Germany. “It was probably round when it formed.”
You’ve got to hand it to Rosetta. By being able to study these images, the many teams of scientists now have evidence for a theory developed last year by Weiss, Elkins-Tanton and MIT’s Maria Zuber. By studying chondrite meteorites, they’ve speculated these strongly magnetized samples most likely occurred in an asteroid with a melted, metallic core. If this theory proves to be correct, the Lutetia simply managed to dodge the proverbial bullets and developed with a molten interior.
“The planets … don’t retain a record of these early differentiation processes,” Weiss says. “So this asteroid may be a relic of the first events of melting in a body.”
According to MIT news, Erik Asphaug, a professor of planetary science at the University of California at Santa Cruz, studies “hit-and-run” collisions between early planetary bodies. He says the work by Weiss and his colleagues is a solid step toward resolving how certain asteroids like Lutetia may have evolved.
“We’ve had decades of cartoon speculation, and here’s speculation that’s anchored in physical understanding of how the interiors of these bodies would evolve,” says Asphaug, who was not involved in the research. “It’s like getting through the first 100 pages of a novel, and you don’t know where it’s leading, but it feels like the beginnings of a coherent picture.”
Radar image of asteroid 2005 YU55, acquired in April 2010. Credit: NASA/Cornell/Arecibo.
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On Tuesday, November 8, at 6:28 p.m. EST, an asteroid the size of an aircraft carrier will soar past our planet at a distance closer than the Moon… and NASA scientists will be watching!
2005 YU55, a 400-meter (1,300-foot) -wide C-type asteroid, was discovered in December 2005 by Robert McMillan of the Spacewatch Program at the University of Arizona, Tucson. It’s pretty much spherical in shape and dark – darker than charcoal, in fact! Scientists with NASA’s Near-Earth Objects Observation Program will begin tracking it on November 4 using the 70-meter radar telescope at the Deep Space Network in Goldstone, California , as well as with the Arecibo Planetary Radar Facility in Puerto Rico beginning November 8. They will continue tracking 2005 YU55 through November 10.
Animation of 2005 YU55's trajectory on Nov. 8. (NASA/JPL) Click to play.
YU55’s orbit is well understood by scientists. It has come this way before, and although this is the closest it’s come to Earth in at least two centuries it will still be at least 324,600 kilometers (201,700 miles) away at nearest approach. That’s about 85% of the distance to the Moon.
It will approach from the sunward side, making viewing in visible light difficult until after it’s made its closest pass.
Other than the excitement it will most likely cause amongst radar astronomers, 2005 YU55 will have no physical effect on our planet. (There have been some rumors circulating online about this particular asteroid’s upcoming pass, in regards to earthquakes and tidal fluctuations and atmospheric disturbances and other such nonsense… the bottom line is that, like the ill-fated comet Elenin, 2005 YU55 has never been known to pose any threat to Earth.)
“YU55 poses no threat of an Earth collision over, at the very least, the next 100 years,” said Don Yeomans, manager of NASA’s Near-Earth Object Program Office at JPL. “During its closest approach, its gravitational effect on the Earth will be so miniscule as to be immeasurable. It will not affect the tides or anything else.”
The 70m telescope at the Goldstone Deep Space Communications Complex in California's Mojave Desert. (NASA/JPL)
Scientists are very eager though to have a prime opportunity to study this quarter-mile-wide world as it makes its closest pass. The giant telescopes at Goldstone and Arecibo will bounce radar waves off the asteroid, mapping its size and shape, and hopefully obtain some very high-resolution images.
“Using the Goldstone radar operating with the software and hardware upgrades, the resulting images of YU55 could come in with resolution as fine as 4 meters per pixel. We’re talking about getting down to the kind of surface detail you dream of when you have a spacecraft fly by one of these targets.”
– Lance Benner, JPL radio astronomer
Even though YU55 will remain at a safe distance the event is still quite notable. The last time an object this large came so close to Earth was in 1976… and scientists weren’t even aware of it at the time. Luckily we now have programs like the Near-Earth Objects Observations Program – a.k.a. “Spaceguard” – to identify asteroids like this, hopefully in time to know if they could become a danger to our planet in either the near or distant future.
As of now, no large space rock with Earth’s name on it has been positively identified… but that doesn’t mean there’s nothing out there either. We need to keep diligent, keep looking and, above all, keep funding programs like this. If anything, this pass should serve as a reminder – however harmless – that we certainly are not alone in the solar system!
Based on an observation posted on the Near Earth Object confirmation page from an image taken by A. D. Grauer using the mount Lemmon observatory, Faulkes telescope team members Nick Howes, Giovanni Sostero and Ernesto Guido along with University of Glamorgan student Antos Kasprzyk and amateur astronomer Iain Melville, imaged what is potentially some of the first direct evidence for a Trojan Jupiter Comet
Comet P/2010 TO20 (LINEAR-GRAUER) was immediately recognised by the team from looking at the orbit to be a highly unusual object, but it was only when the images came through from the faulkes observations that the true nature of the object became clear
The observations showed a distinct cometary appearance, with a sharp central condensation, compact coma and a wide, fan-shaped tail.
This is no ordinary comet, and supports the theory and initial spectral observation work by a team using the keck telescope in Hawaii. Closer analysis of their object (part of a binary known as the Patroclus pair) showed that it was made of water ice and a thin layer of dust, but at the time of writing, no direct images of a Jupiter Trojan showing evidence of a coma and tail had been taken.
The Faulkes teams above image, combined with the original observations by Grauer clearly show a cometary object, thus confirming the Keck team’s hypothesis.
According to the CBET released today “After two nights of observations of Grauer’s comet had been received at the Minor Planet Center.
Spahr realized that this object was identical with an object discovered a year ago by the LINEAR project (discovery observation tabulated below; cf. MPS 351583) that appeared to be a Jupiter Trojan minor planet.”
The observations have now proved it is not a minor planet, but a comet.
This discovery could provide new clues about the evolution of the Solar System, suggesting that the Gas Giants formed closer to the Sun and as they moved further away, they caused massive perturbations with Kuiper Belt objects, trapping some in their own orbits.
Nick Howes on the Faulkes team said “When we first saw the preliminary orbit, we knew it was a quite remarkable object” Howes also added “To have a University Student also involved is terrific for the degree program at Glamorgan and also for the Faulkes project. We’d like to extend our congratulations to Al Grauer” for his detection of this groundbreaking new comet” and we’re immensely proud to be part of the CBET released by the IAU confirming its nature
Southern Hemisphere of Vesta; Rheasilvia and Older Basin. Colorized shaded-relief map showing identification of older 375-kilometer-wide impact basin beneath and overlapping with the more recent Rheasilvia impact structure at asteroid Vesta’s South Pole. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
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Scientists leading NASA’sDawn mission have discovered a 2nd giant impact basin at the south pole of the giant asteroid Vesta, which has been unveiled as a surprisingly “dichotomous” and alien world. Furthermore, the cosmic collisions that produced these two basins shuddered through the interior and created vast Vestan troughs, a Dawn scientist told Universe Today.
The newly discovered impact basin, nicknamed ‘Older Basin’, is actually significantly older in age compared to the initially discovered South Pole basin feature named ‘Rheasilvia’ – perhaps by more than a billion years. And that is just one of the many unexplained mysteries yet to be reconciled by the team as they begin to sift through the millions of bits of new data streaming back daily to Earth.
Scientists speculate that ‘Older Basin’ is on the order of 3.8 Billion years old, whereas ‘Rheasilvia’ might be as young as about 2.5 Billion years, but those are just tentative estimates at this time and subject to change. Measurements so far indicate Rheasilvia is composed of basaltic material.
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
“We found many surprising things at Vesta, which is quite unique and the results have exceeded our expectations”, said Dr. Carol Raymond, Dawn deputy principal investigator, of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
Researchers presented the latest findings from Dawn’s initial science mapping orbit at a news briefing at the annual meeting of the Geological Society of America in Minneapolis, Minn., on Oct. 13.
The team considers Vesta to be the smallest terrestrial planet.
Since achieving orbit in July, Dawn’s Framing Cameras (FC) have imaged most of Vesta at about 250 meter resolution and the Visible and Infrared mapping spectrometer(VIR) at about 700 meter resolution. The measurements were collected at the survey orbit altitude of 2700 km. Before Dawn, Vesta was just a fuzzy blob in humankind’s most powerful telescopes.
Vesta from Hubble (top) as a fuzzy blob and from Dawn in orbit (bottom) in crystal clear high resolution.
Credit: NASA/JPL-Caltech/ UCLA/MPS/DLR/IDA
“There is a global dichotomy on Vesta and a fundamental difference between the northern and southern hemispheres”, said Raymond. “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.”
“There is also a tremendous and surprising diversity of surface color and morphology. The south is consistent with basaltic lithology and the north with impacts. We are trying to make sense of the data and will integrate that with the high resolution observations we are now collecting.”
Indeed Vesta’s completely unique and striking dichotomy can be directly traced back to the basins which were formed by ancient cataclysmic impacts resulting in shockwaves that fundamentally altered the surface and caused the formation of the long troughs that ring Vesta at numerous latitudes.
“The troughs extend across 240 degrees of longitude,” said Debra Buczkowski, Dawn participating scientist, of the Applied Physics Laboratory at Johns Hopkins University, Laurel, Md. “Their formation can be tied back to the two basins at the South Pole.”
Asteroid Vesta and Equatorial Grooves
This full view of the giant asteroid Vesta was taken by NASA’s Dawn spacecraft, as part of a rotation characterization sequence on July 24, 2011, at a distance of 3,200 miles (5,200 kilometers). A rotation characterization sequence helps the scientists and engineers by giving an initial overview of the character of the surface as Vesta rotated underneath the spacecraft. This view of Vesta shows impact craters of various sizes and grooves parallel to the equator. The resolution of this image is about 500 meters per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
In an exclusive follow up interview with Universe Today, Raymond said “We believe that the troughs formed as a direct result of the impacts,” said “The two sets of troughs are associated with the two large basins [Rheasilvia and Older Basin].”
“The key piece of evidence presented was that the set of troughs in the northern hemisphere, that look older (more degraded) are circumferential to the older impact basin,” Raymond told me.
“The equatorial set are circumferential to Rheasilvia. That Rheasilvia’s age appears in places to be much younger is at odds with the age of the equatorial troughs. An explanation for that could be resurfacing by younger mass wasting features (landslides, slumps). We will be working on clarifying all these relationships in the coming months with the higher resolution HAMO (High Altitude Mapping Orbit) data.”
Dawn has gradually spiraled down closer to Vesta using her exotic ion thrusters and began the HAMO mapping campaign on Sept. 29.
Surface features are dated by crater counting methodology.
“Preliminary crater counting age dates for the equatorial trough region yields a very old age (3.8 Billion years). So there is a discrepancy between the apparent younger age for the Rheasilvia basin and the old age for the troughs. These could be reconciled if Rheasilvia is also 3.8 Billion years old but the surface has been modified by slumping or other processes,” Raymond elaborated.
Time will tell as further data is analyzed.
Dawn launch on September 27, 2007 by a Delta II Heavy rocket from Cape Canaveral Air Force Station, Florida. Credit: Ken Kremer
“Vesta is full of surprises, no more so than at the South Pole,” said Paul Schenk at the GSA briefing. Schenk is a Dawn participating scientist of the Lunar and Planetary Institute, Houston, Texas.
The ‘Rheasilvia’ basin was initially discovered in images of Vesta taken a decade ago by the Hubble Space Telescope which revealed it as a gaping hole in the southern hemisphere. But it wasn’t until Dawn entered orbit on July 16, 2011 after a nearly four year interplanetary journey that Earthlings got their first close up look at the mysterious polar feature and can now scrutinize it in detail to elucidate its true nature.
“The South Pole [Rheasilvia] basin is a roughly circular, impact structure and a deep depression dominated by a large central mound,” said Schenk. “It shows sharp scarps, smooth areas, landslide deposits, debris flows. It’s about 475 km in diameter and one of the deepest (ca. 20 -25 km) impact craters in the solar system.”
The central peak is an enormous mountain, about 22 km high and 180 km across- one of the biggest in the solar system. “It’s comparable in some ways to Olympus Mons on Mars,” Schenk stated.
“We were quite surprised to see a second basin in the mapping data outside of Rheasilvia. This was unexpected. It’s called ‘Older Basin’ for now.”
‘Older Basin’ is about 375 km in diameter. They overlap at the place where Rheasilvia has a missing rim.
“These basins are interesting because we believe Vesta is the source of a large number of meteorites, the HED meteorites that have a spread of ages,” Schenk explained.
Images showing key components of Rheasilvia impact basin on Vesta in high resolution ,referred to Shaded-relief topographic map. Credit: NASA/JPL-Caltech/ UCLA/MPS/DLR/IDA
Multiple large impacts over time may explain the source of the HED (Howardite, Eucrite and Diogenite) meteorites.
“We did expect large impacts on Vesta, likely associated with the late heavy bombardment recognized in the lunar impact record,” Raymond told Universe Today. “The surprising element is that the two apparently largest impacts – keeping in mind that other larger impact basins may be lurking under the regolith – are overlapping.”
Dawn’s VIR spectrometer has detected pyroxene bands covering Vesta’s surface, which is indicative of typical basaltic material, said Federico Tosi, a VIR team member of the Italian Space Agency, Rome. “Vesta has diverse rock types on its surface.”
“VIR measured surface temperatures from 220K to 270 K at the 5 micron wavelength. The illuminated areas are warmer.”
So far there is no clear indication of olivine which would be a marker for seeing Vesta’s mantle, Tossi elaborated.
The VIR spectrometer combines images, spectral information and temperature that will allow researchers to evaluate the nature, composition and evolutionary forces that shaped Vesta’s surface.
The team is absolutely thrilled to see a complicated geologic record that’s been preserved for study with lots of apparent surface layering and surprisingly strong and complex structural features with a large range of color and brightness.
Stay tuned for a year of Vestan delights !
Asteroid Vesta from Dawn
South Pole Rheasilvia basin is at lower right. NASA's Dawn spacecraft obtained this image of the giant asteroid Vesta with its framing camera on July 24, 2011 from a distance of about 3,200 miles (5,200 kilometers). Dawn entered orbit around Vesta on July 16, and will spend a year orbiting the body.
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Here’s a great talk given by our friend Phil Plait at a TED event, TEDxBoulder, about how an asteroid might one day give us Earthlings a really bad day. But he’s got good news, too: We have a space program!
