OSIRIS-REx, on its way to a December rendezvous with the potentially dangerous asteroid Bennu, successfully made its second course correction last week.
Rendezvous is scheduled for December 3rd. The probed will orbit the asteroid for about six months, then dive in to get a sample in July 2020, returning it to Earth in 2023.
Researchers and local park volunteers in Botswana’s Central Kalahari Game Reserve on July 8 announced the discovery of a fragment from an asteroid that hit the Earth June 2 only eight hours after it was discovered.
“The biggest uncertainty we faced was to determine where exactly the meteorites fell,” says Peter Jenniskens a subject expert of the SETI Institute in California, who traveled to Botswana to assist in the search. He teamed up with Oliver Moses of the University of Botswana’s Okavango Research Institute (ORI), to gather security surveillance videos in Rakops and Maun to get better constraints on the position and altitude of the fireball’s explosion. Team member Tim Cooper of the Astronomical Society of Southern Africa calibrated videos to the south.
After disruption, the asteroid fragments scattered over a wide area, blown by the wind while falling down. Calculations of the landing area were done independently by the NASA-sponsored group headed by Jenniskens, as well as by Esko Lyytinen and Jarmo Moilanen of the Finnish Fireball Network. These calculations were defining the fall area well enough to warrant the deployment of a search expedition.
The first meteorite was found after five days of walking and scouring a landscape of sand, thick tall grass, shrubs and thorn bushes by a team of geoscientists from the Botswana International University of Science and Technology (BUIST), the Botswana Geoscience Institute (BGI) and from ORI, guided by Jenniskens. The Botswana Department of Wildlife and National Parks granted access and deployed their park rangers to provide protection and participate in the search. BUIST student Lesedi Seitshiro was first to spot the stone.
This is only the second time in history that a small asteroid observed in space was recovered following its impact on Earth.
I have amateur astronomer friends who attempted to do this exact thing, here in Tucson. We actually went out one day hunting for a meteorite they had tracked, but were unsuccessful in finding anything. To have had success we would have likely required more search time and a better constraint on the asteroid’s landing zone.
On Monday the Dawn science team released more close-up images of Ceres, taken from Dawn’s final close orbit of the dwarf planet, with the focus of this release Occator Crater and its bright spots.
The current images now show numerous sections of Occator Crater from an altitude of 35 kilometers and with a resolution less than 5 meters per pixel. “The data exceeds all our expectations,” Dr. Andreas Nathues from the MPS, Framing Camera Lead Investigator, says. In the new images, the surface is now ten times better resolved than in the best images from the previous three years.
Impressive avalanches reveal themselves in the new views of the eastern wall of Occator Crater: there are clear signs that material has been recently moving down the slopes; some of it remains stuck halfway. Other images allow a close look at the interplay of bright and dark material in the eastern part of the crater. “We now hope to understand how the bright deposits outside the crater center came about – and what they tell us about Ceres’ interior,” says Nathues. Various analyses of the past years suggest that Ceres has a water-rich crust. Small impacts and landslides regularly expose ice at the surface, which produces a thin exosphere of water vapor.
I have posted some of these images previously, but there are several new ones at the link.
The uncertainty of science: New observations of interstellar object Oumuamua suggest that it is a comet, not an asteroid.
[B]y combining data from the NASA/ESA Hubble Space Telescope, the Canada-France-Hawaii Telescope, ESO’s Very Large Telescope and the Gemini South Telescope, an international team of astronomers has found that the object is moving faster than predicted. The measured gain in speed is tiny and `Oumuamua is still slowing down because of the pull of the Sun — just not as fast as predicted by celestial mechanics.
The team, led by Marco Micheli (European Space Agency) explored several scenarios to explain the faster-than-predicted speed of this peculiar interstellar visitor. The most likely explanation is that `Oumuamua is venting material from its surface due to solar heating — a behaviour known as outgassing. The thrust from this ejected material is thought to provide the small but steady push that is sending `Oumuamua hurtling out of the Solar System faster than expected — as of 1 June, it is travelling with about 114 000 kilometres per hour.
Such outgassing is a typical behaviour for comets and contradicts the previous classification of `Oumuamua as an interstellar asteroid. “We think this is a tiny, weird comet,” comments Marco Micheli. “We can see in the data that its boost is getting smaller the farther away it travels from the Sun, which is typical for comets.”
If I was to speculate wildly, I could also wonder if maybe the aliens on board have decided they needed to get the heck out of here as fast as possible, and have fired their thrusters to make that happen.
Cool image time! Dawn, now in its final very close orbit above the surface of Ceres, has released some new images. The image on the right, cropped to post here, was taken from a distance of only 22 miles, and shows a fracture network and some very pronounced cliffs on the wall of Occator Crater. The sunlight is coming from the right. You can also see a bright spot on an east-facing slope with what looks like an apron of lighter avalanche material below it. The flat smooth surface of the floor of this same canyon is likely because it is filled with dust, which has ponded there.
These fractures suggest that the wall of the crater is undergoing a slow motion avalanche, with sections separating off and slowly sagging into the crater below, creating the fractures.
Japan’s Hayabusa-2 probe has officially completed its rendezvous with Ryugu, and is now flying about 12 miles above its surface.
Now comes the really hard part, finding landing locations for its MASCOT lander, its three other tiny rovers, and for Hayabusa-2 itself, so it can grab its sample for the return journey.
The Hayabusa-2 science team has released its first image of Ryugu, posted to the right, from a distance of only 25 miles. From the project manager:
The shape of Ryugu is now revealed. From a distance, Ryugu initially appeared round, then gradually turned into a square before becoming a beautiful shape similar to fluorite [known as the ‘firefly stone’ in Japanese]. Now, craters are visible, rocks are visible and the geographical features are seen to vary from place to place. This form of Ryugu is scientifically surprising and also poses a few engineering challenges.
First of all, the rotation axis of the asteroid is perpendicular to the orbit. This fact increases the degrees of freedom for landing and the rover decent operations. On the other hand, there is a peak in the vicinity of the equator and a number of large craters, which makes the selection of the landing points both interesting and difficult. Globally, the asteroid also has a shape like fluorite (or maybe an abacus bead?). This means we expect the direction of the gravitational force on the wide areas of the asteroid surface to not point directly down. We therefore need a detailed investigation of these properties to formulate our future operation plans.
They are going to have to spend some time in orbit to figure out not only where to land, but how to do it. More information on the mission can be found here.
Hayabusa-2 has moved to within 23 miles of the asteroid Ryugu and is expected to reach its planned 12 mile rendezvous distance on June 27.
No new pictures, though I wouldn’t be surprised if some showed up today or tomorrow.
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Cool image time! Hayabusa-2’s approach to asteroid Ryugu continues. The image to the right, cropped to post here, shows one of four images taken by the spacecraft on June 17 and June 18. In this image the distance is about 150 miles. As noted in the Hayabusa-2 press release,
The shape of the asteroid looks like a spinning top (called a “Coma” in Japanese), with the equatorial part wider than the poles. This form is seen in many small asteroids that are rotating at high speed. Observed by radar from the ground, asteroid Bennu (the destination of the US mission, OSIRIS-REx), asteroid Didymous (the target of the US DART project), and asteroid 2008 EV5 that is approaching the Earth, all have a similar shape.
On the surface of asteroid Ryugu, you can see a number of crater-like round recessed landforms. In the first image, one large example can be seen with a diameter exceeding 200m. This moves to the left and darkens as the asteroid rotates and the lower part becomes cast in shadows.
The bulge at the equator forms a ridge around the asteroid like a mountain range. Outside this, the surface topology appears very ridge-shaped and rock-like bulges are also seen. These details should become clearer as the resolution increases in the future.
Based on the visible landforms, they presently estimate Ryugu’s rotation period to be about 7.5 hours.
A computer entrepreneur has raised questions about the data analysis used by the scientists in charge of NASA’s NEOWISE space telescope (formerly called the Wide-field Infrared Space Telescope, or WISE).
Myhrvold, a former chief technologist for Microsoft, founded the patent-buying firm Intellectual Ventures in Bellevue, Washington, in 2000; on the side, he pursues interests ranging from modernist cuisine to palaeontology. A few years ago, he began exploring ways to detect dangerous space rocks. He soon argued3 that the Large Synoptic Survey Telescope, a ground-based telescope being built in Chile, would have the capacity to find nearly all the same asteroids as NASA’s proposed successor to NEOWISE, called NEOCam.
That turned his attention to how asteroids could be studied in space, and to the NEOWISE data. “I thought, this will be great, maybe we’ll be able to find some new and interesting things in here,” he says. But Myhrvold soon became frustrated with the quality and analysis of the data. He posted a critical preprint on arXiv in May 2016, and the peer-review game was on.
His first peer-reviewed critique was published in Icarus in March4. In it, he explored the mathematics of how asteroids radiate heat, and said that the NEOWISE team should have accounted for such effects more thoroughly in its work.
The latest paper1 holds the bulk of the NEOWISE critique. Among other things, Myhrvold argues that the NEOWISE team applied many different modelling techniques to many different combinations of data to achieve its final results. He also criticizes the choice to include previously published data on the diameter of certain asteroids in the data set, rather than using NEOWISE measurements — which, though less precise, are at least consistent with the rest of the database. Such choices undermine the statistical rigour of the database, he says.
Alan Harris, a planetary scientist with the consulting firm MoreData! in La Cañada Flintridge, California, was one of the paper’s reviewers. “In my opinion, it has important things to say,” he says. “It is my hope that the scientific community will read the paper and pay attention to the analysis Myhrvold has presented, as he has raised a number of significant issues.”
The disagreement involves the NEOWISE team’s estimate of asteroid sizes, based on the infrared data. Myhrvoid questions their estimates.
More details about the clashes between Myhrvoid and the NEOWISE science team over the past two years can be found here. The NASA scientists do not come off well. They appear to be very defensive, acting to stonewall any review of their work. Repeatedly they attempted to defy Myhrvoid’s FOIA requests (only made when they refused to release their raw data), including redacting significant information for no justifiable reason.
I have really only one question: Does the behavior of these NASA planetary scientists sound familiar? To me it does, and what it reminds me of speaks very badly for the science being done in the NEOWISE mission at NASA.
Cool image time! With Dawn completing its descent into its final low orbit only about 30 miles above the surface of Ceres, it is beginning to take some very spectacular images. Above is a cropped section from a full image taken on June 9th of the rim of Occator Crater from an altitude of 27 miles. It shows evidence of landslides on the crater’s rim, as well as at least two bright patches. If you click on it you can see the entire picture.
Nor is this the only cool image released As Dawn descended to its new orbit, it took one very cool oblique image of the planet’s horizon. On the right I have cropped a small section out of one such image, taken on May 30th from an altitude of 280 miles. If you click on it you can see the full image, showing numerous other small craters all around it, to the horizon.
Note the bright streaks on the crater walls, suggestive of more landslides as well as seepage of the thought-to-exist brine from below the surface.
For the next year or so, as Dawn winds down its mission, expect a lot more very intriguing pictures of Ceres. I am especially eager to see close-ups of the bright spots at the center of Occator Crater.
The uncertainty of science: A new analysis of data from Dawn now suggests that the surface of Ceres has a greater percentage of organic molecules than previously estimated.
To get an initial idea of how abundant those compounds might be, the original research team compared the VIR data from Ceres with laboratory reflectance spectra of organic material formed on Earth. Based on that standard, the researchers concluded that between six and 10 percent of the spectral signature they detected on Ceres could be explained by organic matter.
But for this new research, Kaplan and her colleagues wanted to re-examine those data using a different standard. Instead of relying on Earth rocks to interpret the data, the team turned to an extraterrestrial source: meteorites. Some meteorites — chunks of carbonaceous chondrite that have fallen to Earth after being ejected from primitive asteroids — have been shown to contain organic material that’s slightly different from what’s commonly found on our own planet. And Kaplan’s work shows that the spectral reflectance of the extraterrestrial organics is distinct from that of terrestrial counterparts.
“What we find is that if we model the Ceres data using extraterrestrial organics, which may be a more appropriate analog than those found on Earth, then we need a lot more organic matter on Ceres to explain the strength of the spectral absorption that we see there,” Kaplan said. “We estimate that as much as 40 to 50 percent of the spectral signal we see on Ceres is explained by organics. That’s a huge difference compared to the six to 10 percent previously reported based on terrestrial organic compounds.”
Please note: Both estimates depend on assumptions that could easily be wrong. Ceres might have less organics, or more, than either estimate. Or somewhere in the middle. These estimates are merely educated guesses.
And remember, organic molecules does not mean life. It only means the molecules use carbon as a component.
