ESA Rosetta - Lutetia's Lineaments: Dark side of asteroid hosts hidden crater

ESA's Rosetta spacecraft data. Tracing Lutetia’s grooves.

Credit: ESA /Rosetta /MPS for OSIRIS Team MPS /UPD /LAM /IAA /SSO /INTA /UPM /DASP /IDA

Grooves found on Lutetia, an asteroid encountered by ESA's Rosetta spacecraft, point to the existence of a large impact crater on the unseen side of the rocky world.

ESA's Rosetta spacecraft flew past Lutetia at a distance of 3168 km in July 2010, en route to its 2014 rendezvous with its target comet.

The spacecraft took images of the 100 km-wide asteroid for about two hours during the flyby, revealing numerous impact craters and hundreds of grooves all over the surface.

Impact craters are commonly seen on all Solar System worlds with solid surfaces, recording an intense history of collisions between bodies. However, grooves are much less prevalent.

To date, they have been discovered by visiting spacecraft only on the Martian moon Phobos and the asteroids Eros and Vesta.

The way in which grooves are formed on these bodies is still widely debated, but it likely involves impacts.

Shock waves from the impact travel through the interior of a small, porous body and fracture the surface to form the grooves.

"For Lutetia, by assuming that the grooves were formed in concentric patterns around their source impact crater, we identified 200 such features falling into distinct 'families', correlated with three different impact craters," describes Sebastien Besse, a research fellow at ESA's Technical Centre, ESTEC, in the Netherlands, and lead author of the paper published in Planetary and Space Science this month.

One of the groove systems on Lutetia is associated with the Massilia crater and another with the North Pole Crater Cluster, which comprises a number of superimposed craters. Both are on the asteroid's northern hemisphere.

This anaglyph 3D image of Lutetia can be viewed using stereoscopic glasses with red–green or red–blue filters. 

The two images making up this image were taken several minutes before Rosetta’s closest approach to the asteroid on 10 July 2010. 

The left-eye view was captured at 15:41:39 GMT from a distance of 4274 km from Lutetia’s surface and the right-eye view at 15:41:03 GMT from 4038 km (closest approach was at 15:45 GMT). 

Credit: ESA/H. Sierks (MPS, Göttingen, Germany)

But another group of grooves points to a crater not seen during Rosetta's brief flyby, in the asteroid's southern hemisphere.

Its implied presence has earned it the nickname 'Suspicio'. The grooves related to Suspicio cover a large area on the asteroid, suggesting it may span several tens of kilometres .

By comparison, Massilia, the largest known crater on Lutetia, is about 55 km wide, and the largest of the polar cluster is about 34 km across.

"These three major impacts seriously deformed Lutetia's surface," adds Sebastien.

Looking face on at the North Pole Crater Cluster (purple outline) on asteroid Lutetia, with Massilia crater to the lower left (red outline). 

Marked on the image are the concentric grooves or ‘lineaments’ associated with the large craters. 

The lineaments coloured blue infer the presence of a large crater, nicknamed Suspicio, on the unseen portion of Lutetia. 

Yellow denotes lineaments not associated with any of the craters discussed in this study. 

Credit: ESA /Rosetta /MPS for OSIRIS Team MPS /UPD /LAM /IAA /SSO /INTA /UPM /DASP /IDA

"As with grooves seen on other asteroids that may also be associated with impact events, this study provides new insights into the catastrophic history of these small bodies."

By observing how subsequent small craters lie over the grooves on Lutetia, the scientists determined the relative ages of the three larger cratering events.

Massilia is thought be the oldest of the three craters and the polar cluster the youngest, with Suspicio between.

The authors also looked at other, independent measurements of Lutetia, including ground-based observations with the Infrared Telescope Facility and space-based observations with ESA's Herschel and NASA's Spitzer.

The infra-red location of Suspicio crater on the unseen southern hemisphere of asteroid Lutetia (marked in blue). 

The hidden crater could be up to 45 km in diameter, the blue outlines correspond to diameter estimates of 15, 30 and 45 km, respectively. 

The crater is inferred based on the numerous grooves or ‘lineaments’ seen concentric to the crater in the northern hemisphere of the asteroid. 

There are no image data available for this side of the asteroid, as can be inferred from the blank shape model. 

Credit: ESA /Rosetta /MPS for OSIRIS Team MPS /UPD /LAM /IAA /SSO /INTA /UPM /DASP /IDA

The Infrared Telescope Facility suggested different compositions between the northern and southern hemisphere of the asteroid.

Sebastien and his colleagues propose that a large impact, presumably the one forming Suspicio, excavated enough material of a different composition to account for the observed differences.

"Our study ties together several independent analyses of Lutetia into one coherent story that is consistent with the presence of a large impact crater on the far side of the asteroid," says co-author Michael Küppers, from ESA's Space Astronomy Centre in Spain.

"Four years on and we are delighted still to be learning from just two hours' worth of data collected during the Lutetia flyby," says Matt Taylor, ESA's Rosetta project scientist.

"Rosetta is now in its main mission phase at its comet, where we are on the cusp of fantastic results. Rosetta is a true small bodies mission, two asteroids and one comet in single trip."

More information: S. Besse, M. Küppers, O.S. Barnouin, N. Thomas, J. Benkhoff, "Lutetia׳s lineaments," Planetary and Space Science, Volume 101, 15 October 2014, Pages 186-195, ISSN 0032-0633, dx.doi.org/10.1016/j.pss.2014.07.007

Dark Side: Australian team maps Moon's hidden craters

Some 66 of the possible 280 additional craters on the Moon, in a photo from Western Australia's Curtin University in Perth released on June 18, 2013. 

Australian scientists Tuesday said they had identified a possible 280 additional craters on the Moon, a finding they said could shed light on the history of the Earth's natural satellite.

Australian scientists Tuesday said they had identified a possible 280 additional craters on the Moon, a finding they said could shed light on the history of the Earth's natural satellite.

By combining gravity and topography data collected by satellites, the scientists from Curtin University in Western Australia were able to use computer modelling to at first identify two basins on the far side of the Moon.

They later developed a high-resolution image to find a total of 280 "candidate basins" which they suspect are craters.

Will Featherstone

"There are many more (craters) that have been mapped from optical observations or from just the shape of the topography," researcher Will Featherstone told reporters.

"So there's many, many craters that were already known, we've just been able to apply this technique to enhance the ones that aren't so easy to see.

"What we have been able to use is the topography and the gravity together to get a stronger indication that there is something there that needs further investigation."

Featherstone said the researchers looked at the lunar surface on both the near and far sides of the Moon, the dark side being more challenging because satellites cannot be tracked from Earth when they are on that side.

To get around this, the researchers used data gathered from a mission which used multiple satellites which were tracking each other as they circled the Moon.

"So when the satellite orbiting the Moon went behind the far side and they couldn't be seen from Earth, they could be seen by other satellites," he said.

Featherstone said of the 280 possible craters, the researchers had classified 66 of them as distinctly visible according to both gravity and topography.

"Scientists can, instead of looking at every square inch of the Moon looking for basins, they can target these areas," he said.

"It just helps investigations of the Moon and the history of the Moon and the solar system," he added.

The team has also done some work on the gravity of Mars and Featherstone said other data sets were also available for Venus and other planets.

He said scientists were optimistic about further discoveries from applying their techniques to new gravity data from NASA's GRAIL mission, which ended in late 2012 when the two satellites - named Ebb and Flow - were deliberately crashed on the Moon.

Mysterious electron Cluster found hidden among Van Allen belts

This NASA rendering depicts Earth's Van Allen radiation belts and the path of the Van Allen Probe spacecraft, which were launched in August 2012. 

Data from the spacecraft have confirmed a never-before-seen phenomenon-a long-lived zone of high-energy electrons residing between the inner and outer radiation belts. (Credit: NASA illustration)

U.S. researchers, including a trio from Los Alamos National Laboratory, have witnessed the mysterious appearance of a relatively long-lived zone of high-energy electrons stored between Earth's Van Allen radiation belts.

The surprising findings, discovered by NASA's Van Allen Probes (formerly known as the Radiation Belt Storm Probes), were outlined Thursday in Science Express and during a press conference at NASA headquarters in Washington, D.C.

The research was led by Dan Baker of the University of Colorado, Boulder, Laboratory for Atmospheric and Space Physics.

"Nature keeps on surprising us by producing long-lived harsh environments in space in regions not previously considered," said Los Alamos plasma physicist Reiner Friedel of LANL's Intelligence and Space Research Division. "This finding may impact the planning of future space missions."

The Van Allen radiation belts - named in honor James Van Allen, who discovered them nearly 50 years ago - are a pair of donut shaped zones of charged particles that surround Earth and occupy the inner region of our planet's Magnetosphere.

The outer belt contains extremely high-energy electrons, while the inner belt is comprised of energetic protons and electrons.

The belts have been studied extensively since the dawn of the Space Age, because the high-energy particles in the outer ring can cripple or disrupt spacecraft. Long-term observation of the belts have hinted that the belts can act as efficient and powerful particle accelerators; the recent observations by the Van Allen Probes-a pair of spacecraft launched in August 2012-now seem to confirm this.

Shortly after launch, the spacecraft activated their Relativistic Electron-Proton Telescope (REPT) instruments to measure particles within the belts and their immediate environs.

The instrument immediately detected on September 1, 2012, the presence of a stable zone of high-energy electrons residing between the belts. This donut-shaped third ring nestled between the belts existed for nearly a month before being obliterated by a powerful shockwave of particles emanating from center of the solar system.

Such a distinct, long-lasting ring of high-energy electrons had never before been seen by any prior instrument in space or on Earth.

The findings suggest that the Van Allen Belts somehow capture and store energetic electrons in a circular path around our home planet, perhaps in much the same way as a cyclotron can capture and store charged particles here on Earth.

"One of the main reasons the Van Allen Probe instruments are seeing these new features are their unprecedented sensitivity and rejection of backgrounds," Friedel said.

"As the mission proceeds, we expect further surprises that will challenge our conventional wisdom on the transport, loss and energization processes in these highly energetic electron radiation regions."

NASA Hubble finds Jupiter's hidden Stripe

New Hubble images reveal what happened to one of Jupiter’s main cloud belts: It’s hiding behind ammonia clouds.

“Weather forecast for Jupiter’s Southern Equatorial Belt: cloudy with a chance of ammonia,” planetary scientist Heidi Hammel of the Space Science Institute in Boulder, Colorado said in a press release Wednesday.

The gas giant’s characteristic band of dark clouds started fading late last year and had vanished completely by early May, 2010.

Images taken with Hubble’s Wide Field Camera 3 on June 7 — just over three days after an unknown object smacked into the planet — found a layer of white ammonia ice crystal clouds. The ammonia clouds float at a higher altitude than the missing brown clouds, obscuring them from view.

The images show a preview of what’s to come for the dark stripe, too. A chain of dark spots along the boundary of Jupiter’s south tropical zone peek through the white cloud layer as the ammonia thins and dissipates.

“The Hubble images tell us these spots are holes resulting from localized downdrafts. We often see these types of holes when a change is about to occur,” said planetary scientist Amy Simon-Miller of NASA.

The clouds blocking the famous equatorial stripe should clear out similarly in a couple of months, the team predicts.

“The Southern Equatorial Belt last faded in the early 1970s. We haven’t been able to study this phenomenon at this level of detail before,” Simon-Miller added. “The changes of the last few years are adding to an extraordinary database on dramatic cloud changes on Jupiter.”



The images also provided clues to the identity of the mystery object that hit Jupiter on June 3.

A lack of dark debris at the impact site, which would have been kicked up by the object exploding beneath the clouds, suggests that the object was relatively small and burned up in Jupiter’s atmosphere like a meteor.

“Hubble was only one of several observatories that looked for signs of Jupiter’s impact scar, with more results on their way,” planetary scientist Leigh Fletcher of the University of Oxford noted on Twitter. “Gemini, Keck, VLT and IRTF were all racing to find signs of the impact within hours of the event taking place.”

Iran's Hidden Nuclear Facility - Interactive MAP Feature - NYTimes.com

Iran?s Hidden Nuclear Facility - Interactive Feature - NYTimes.com

Iran's Hidden Nuclear Facility

Images show the details of a hidden facility in Iran that experts say is the nuclear site recently disclosed by the Obama administration. Information about the plant is from an analysis by IHS Jane's.

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