Tag: science

Wormlike glacier on Mars

9:30 am

Glacial flow in the mid-latitude southern cratered highlands
Click for full image.

Cool image time! The image to the right, cropped and reduced to post here, shows a very typical glacial-type feature found frequently in the mid-latitudes of Mars. Taken on May 23, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), it is labeled a “Lobate Flow Feature within Channel in Nereidum Montes.” Nereidum Montes is a rough mountainous region along the northwestern margin of Argyre Basin, the second largest impact basin on Mars, after Hellas Basin.

Scientists using Europe’s Mars Express orbiter have already found a great deal of glacial evidence in these mountains. I have also posted images of other glacial features on the north edge of Argyre. This image just reinforces that data.

This particular glacier however resembles the kind of glaciers one sees on Earth more than most Martian glaciers. As it meanders down its valley, large cracks form near its edges as friction slows their passage and drags them apart. In fact, the glacier itself might have very well carved the canyon. According to Dan Berman, senior scientist at the Planetary Science Institute in Arizona, who had requested this image,

While I can’t say for sure, the canyon was likely formed by a glacier. Whether or not the ice that remains today is part of that glacier, or one that formed later, is impossible to say.

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The colors of Mars

1:07 pm

The different colors of Mars
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Actually today’s cool image tells us less about the real colors on Mars and much about the colors captured by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The photo on the right was taken on May 2, 2020, and shows a relatively featureless area to the east of 80-mile wide Byrd Crater in the high southern latitude of Mars.

The only major features seen on this photo are a series of rounded ridges that in the larger context map at the image site look almost like drainage hollows coming down from the crater’s rim about twenty miles away.

The colors, though exaggerated and not entirely as the eye would see them, still tell us something very real about the surface. As explained here [pdf]:

In spite of the variable level of color enhancement for the Extras products, we can make some generalizations to better understand what the stretched color images are showing. Dust (or indurated dust) is generally the reddest material present and looks reddish in the RGB color. … Coarser-grained materials (sand and rocks) are generally bluer … but also relatively dark, except where coated by dust. Frost and ice are also relatively blue, but bright, and often concentrated at the poles or on pole-facing slopes. Some bedrock is also relatively bright and blue, but not as much as frost or ice, and it has distinctive morphologies.

Thus, this photo is telling us that the lower areas are covered with dust (the red), while the rounded ridgelines are covered with coarser and bigger rocks. The brightest blue, which is facing towards the south pole, might also indicate frost or ice.
» Read more

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Report: Astronomy threatened by satellite constellations

11:31 am

A report issued today, resulting from a video conference of astronomers in July, has concluded that much of ground-based astronomy is threatened by the new large satellite constellations being launched by SpaceX, OneWeb, and others.

The astronomers’ report offers six solutions for solving the problem.

  • Launch fewer or no LEOsats. However impractical or unlikely, this is the only option identified that can achieve zero astronomical impact.
  • Deploy satellites at orbital altitudes no higher than ~600 km.
  • Darken satellites or use sunshades to shadow their reflective surfaces.
  • Control each satellite’s orientation in space to reflect less sunlight to Earth.
  • Minimize or eventually be able to eliminate the effect of satellite trails during the processing of astronomical images.
  • Make more accurate orbital information available for satellites so that observers can avoid pointing telescopes at them.

Notice what solution they don’t offer? Maybe astronomy should focus on building space-based telescopes, where the view would be clear, unimpeded by both the satellites and (much more importantly) the atmosphere.

In fact, the claim in the first solution above, that launching no satellites is “the only option identified that can achieve zero astronomical impact” is intellectually dishonest. All astronomers have to do is get their observatories into space, something that is very doable and affordable with today’s cheaper launch capabilities and technology. In space the impact of the satellites will once again be zero. And they will have the added benefit of getting outside the atmosphere, which by the way is actually a bigger limitation to observations than any satellite constellation.

It seems to me that this report was written by the faction of astronomers who make their living building big ground-based telescopes. Rather than think of solutions, they want to protect their turf by attacking the achievements of others.

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Hubble photographs Comet NEOWISE

12:38 pm

Comet NEOWISE, photographed by the Hubble Space Telescope
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Using the Hubble Space Telescope, astronomers have obtained close-up images of Comet NEOWISE after it had survived its closest approach to the Sun. The photo to the right, cropped and reduced to post here, is one of Hubble’s two images.

Comets often break apart due to thermal and gravitational stresses at such close encounters, but Hubble’s view suggests that NEOWISE’s solid nucleus stayed intact. This heart of the comet is too small to be seen directly by Hubble. The ball of ice may be no more than 4.8 kilometres across. But the Hubble image does captures a portion of the vast cloud of gas and dust enveloping the nucleus, which measures about 18 000 kilometres across in this image.

Hubble’s observation also resolves a pair of jets from the nucleus shooting out in opposite directions. They emerge from the comet’s core as cones of dust and gas, and then are curved into broader fan-like structures by the rotation of the nucleus. Jets are the result of ice sublimating beneath the surface with the resulting dust/gas being squeezed out at high velocity.

Below the fold is a six-second movie made of Hubble’s two images, showing how the jets changed over a three hour time period on August 8th.
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Mars: On the floor of Valles Marineris

11:50 am

Strange flow (?) on floor of Valles Marineris
Click for full image.

Cool image time! The image to the right, rotated and cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on May 14, 2020, and shows a very strange bright outcrop on the floor of Valles Marineris, the largest canyon on both Mars and in the entire solar system.

MRO has photographed this spot a few times since 2007. The first image was posted with a detailed caption by Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona, who described the feature like so:

Most of the material is light and shows many small scarps or benches. In places these appear to indicate boundaries between layers, but they are often discontinuous. The light material is buried by a thin mantle of dark material in places; the dark material is from other rock layers—possibly those above the outcrop—and has fallen or been blown over the light rock.

Near the top of the outcrop, there is a distinctive layer that appears as a dark band at low resolution. At the full resolution of HiRISE, this appears to be a layer breaking up into angular boulders, indicating different rock properties than the underlying light rock. There does appear to be some light material above this layer, suggesting that the process that deposited the light material continued for some time.

Dundas also added that the lighter material is theorized to have “formed by a variety of processes. Proposed deposition mechanisms for light-toned sediments on Mars include those from rivers or lakes, volcanic ash or wind-blown sand or dust.”

Since this lighter colored outcrop has remained as bright as it has now for more than six Martian years, I doubt it is brighter because of the surface deposit of ash, sand, or dust (though it might be made of these materials which have now become hardened). My guess is that the brightness is inherent to the outcrop. Moreover, note the plateau to the southwest. Its rim is cut sharply, suggesting erosion revealed this outcrop, and that the outcrop is made of more resistant material.

The overview map provides some context that also might help explain the geology at this location.
» Read more

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Tests this weekend to pinpoint slow leak on ISS

1:08 pm

The astronauts this weekend will shut all the hatches between different modules on ISS so that ground controllers can try to pinpoint the location of a long term slow air leak.

This leak was first spotted in September 2019, when there were “indications of a slight increase above the standard air leak rate,” NASA said in the statement. “Because of routine station operations like spacewalks and spacecraft arrivals and departures, it took time to gather enough data to characterize those measurements. That rate has slightly increased, so the teams are working a plan to isolate, identify and potentially repair the source.”

While the leak rate is higher than usual, it is still within specifications for the station and poses no immediate danger to the crew, NASA officials emphasized. Astronauts also deal with leak simulations during training for their stays on the space station, which typically are about six months long.

The weekend test will allow them to identify where the leak is located. They will then be better able to find it, and mitigate it.

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Movie of OSIRIS-REx’s last rehearsal before sample grab

3:53 pm

Closest point to Nighingale landing site during OSIRIS-REx's last rehearsal
Click image for full movie.

The OSIRIS-REx science team has released a movie made by the spacecraft’s navigation camera during its August 11th final rehearsal prior to the planned sample grab-and-go now set for October.

The image to the right is a capture of one image when the spacecraft was closest to the asteroid, about 131 feet above the surface. The target landing site, dubbed Nightingale, is the somewhat smooth area near the top half of the frame.

These images were captured over a three-hour period – the imaging sequence begins approximately one hour after the orbit departure maneuver and ends approximately two minutes after the back-away burn. In the middle of the sequence, the spacecraft slews, or rotates, so that NavCam 2 looks away from Bennu, toward space. Shortly after, it performs a final slew to point the camera (and the sampling arm) toward the surface again. Near the end of the sequence, site Nightingale comes into view at the top of the frame. The large, tall boulder situated on the crater’s rim (upper left) is 43 feet (13 meters) on its longest axis. The sequence was created using nearly 300 images taken by the spacecraft’s NavCam 2 camera.

Nightingale might be their best choice, but it remains about half the size they had originally wanted for their grab-and-go site, with far too many objects larger than planned. They designed the grab-and-go equipment to catch objects smaller than 0.8 inches. Little at this location, or on the entire surface of Bennu, is that small. The asteroid is truly a pile of gravel, with no dust.

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Hope completes first course correction on trip to Mars

3:24 pm

The new colonial movement: The United Arab Emirates’ (UAE) Mars Hope orbiter has successfully completed its first course correction on its journey to Mars.

The success of this maneuver is a big deal, as it appears it was controlled from the UAE’s control center by its engineers. Up to now this project has mostly been a joint U.S/UAE project, launched by Japan, with U.S. universities doing the heavy lifting while training UAE personnel. Now the UAE engineers are in charge, and so they have to get it right.

They have another half dozen course corrections scheduled before arrival in February 2021, when the spacecraft will have its big maneuver, entering Martian orbit.

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Majestic dunes on Mars

11:26 am

Beautiful dunes on Mars
Click for full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on May 10, 2020, and shows the dune field inside a large unnamed sixty-mile-wide crater in the highlands of Mars.

Scientists have been using MRO to monitor this site to track both dust devils and dune changes since at least 2009. In 2009 the focus was on the numerous dust devil tracks, and in fact I posted in March 2020 a comparison of an earlier image with a more recent picture, showing how the earlier tracks had vanished in recent pictures, probably wiped clean by the global dust storm in 2018.

This time however I am less interested in the science, which I covered in detail in that previous post, but in the beauty of these dunes. They are large and majestic, and the color strip tells us that they exhibit striking colors of green, gold, and tan. Is there a place on Earth with dunes of such colors? If so, it is rare.

Make sure you click on the image to see the full resolution photograph. It is even more breath-taking.

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Tiny asteroid sets record for closest fly-by of Earth

9:10 am

Astronomers using the robotic Zwicky Transient Facility (ZTF) at the Palomar Observatory in California on August 16 spotted a tiny asteroid just after it had zipped past the Earth at a distance of only 1,830 miles, the closest any asteroid has ever been seen to do so without hitting the ground.

Asteroid 2020 QG is about 10 to 20 feet (3 to 6 meters) across, or roughly the size of an SUV, so it was not big enough to do any damage even if it had been pointed at Earth; instead, it would have burned up in our planet’s atmosphere.

“The asteroid flew close enough to Earth that Earth’s gravity significantly changed its orbit,” says ZTF co-investigator Tom Prince, the Ira S. Bowen Professor of Physics at Caltech and a senior research scientist at JPL, which Caltech manages for NASA. Asteroids of this size that fly roughly as close to Earth as 2020 QG do occur about once a year or less, but many of them are never detected.

The ability to spot these things is continuing to improve, though it does not appear they have yet obtained enough information to predict 2020 QG’s full orbit, or when or if it will return.

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Mars: A small volcano at the base of a big volcano

1:31 pm

Volcanic vent near Pavonis Mons
Click for full image.

Today’s cool image is of a recent high resolution image taken on May 30, 2020 by Mars Reconnaissance Orbiter (MRO) of what they label as a volcanic vent near Pavonis Mons, the middle giant volcano in the string of three that sit between Olympus Mons, the biggest Martian volcano in the solar system, and Valles Marineris, the biggest canyon in the solar system.

MRO took a previous picture of this vent back in 2010, when they labeled it instead a “small volcano.” Both labels are essentially correct. The two depressions here clearly were a vent for lava at some point in the past. The depressions also fit the definition of a small volcano, as they sit at a high point with two rills flowing down from them. In some ways they could be considered small calderas at the top of a volcano.
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Rocket Lab planning private Venus mission

8:33 am

Capitalism in space: According to its founder and CEO Peter Beck, the smallsat rocket company Rocket Lab is now planning a private Venus mission to be launched in 2023.

The 2023 mission will employ Rocket Lab’s two-stage Electron booster and Photon satellite bus. The 57-foot-tall (17 meters) Electron is a viable option for interplanetary missions now, thanks to recent advances in battery technology that boost the performance of the rocket’s Rutherford engines. With that improvement, Electron is now capable of lofting up to 660 lbs. (300 kilograms) of payload to low-Earth orbit instead of 500 lbs. (225 kg), Rocket Lab representatives have said.

“It opens the window for Venus, and it opens the window for recovery,” Beck said. (The company is working to recover and reuse the Electron’s first stage. Returning boosters will make guided re-entries to Earth’s atmosphere, which will require more fuel, which in turn will require more powerful engines to get the added weight off the ground.)

Photon, which has yet to make its spaceflight debut, won’t descend into Venus’ sulfurous skies on the coming mission. The current plan calls for the spacecraft to deploy one or more smaller probes into the planet’s atmosphere, Beck wrote in a Twitter post on Aug. 4.

There is a certain irony here, if Beck launches a private interplanetary science mission ahead of Elon Musk. Musk created the rocket company SpaceX expressly because he wanted to do a private science mission to Mars and needed an affordable rocket to do it. Since then he has been so focused on making that rocket company succeed he has not devoted any effort to that initial science mission concept. Beck, who came much later, now appears set to beat Musk to this first milestone.

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Bottom edge of Martian glacier?

1:53 pm

The foot of an inactive glacier on Mars
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Today’s cool image, taken on May 25, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), provides a nice example of the typical foot of an inactive buried glacial flow on Mars. The image to the right, rotated, cropped, and reduced to post here, focuses on the center of the full image. Uphill is to the right. The glacier’s edge runs down the middle left of the photo.

Scientists call this a lobate flow because its shape resembles a lobe, smooth and rounded as it comes down the slope. Located at 38 degrees south latitude to the east of Hellas Basin and just to the north of one of that basin’s major infeeding canyons, Harmakhis Valles, this flow comes down the west side of a large mountain. The overview map below provides the context, with the white rectangle indicating the photo’s location.
» Read more

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Juno’s 28th fly-by of Jupiter

10:20 am

Cool movie time! Below is a short movie created by citizen scientist Gerald Eichstädt from images taken by Juno as it swung past Jupiter on its 28th close pass since arriving in orbit in 2016.

In natural colors, Jupiter looks pretty pale. Therefore, the still images are approximately illumination-adusted, i.e. almost flattened, and consecutively gamma-stretched to the 4th power of radiometric values, in order to enhance contrast and color.

Like for all its previous flybys, Juno approached Jupiter roughly from north, and left Jupiter looking towards the soutern hemisphere. Closest approach to Jupiter was 3,500 km above the nominal IAU 1-bar level, and near 25.3 degrees north (planetocentric), according to long-term planning of November 2017.

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Oumuamua wasn’t made of hydrogen ice

9:45 am

The uncertainty of science: According to a new paper published today, Oumuamua wasn’t a hydrogen iceberg as proposed by other scientists earlier this year.

Traveling at a blistering speed of 196,000mph in 2017, ‘Oumuamua was first classified as an asteroid, and when it later sped up, was found to have properties more akin to comets. But the 0.2km radius interstellar object didn’t fit that category, either, and its point of origin has remained a mystery. Researchers focused on the giant molecular cloud (GMC) W51—one of the closest GMCs to Earth at just 17,000 light years away—as a potential point of origin for ‘Oumuamua, but hypothesize that it simply could not have made the journey intact. “The most likely place to make hydrogen icebergs is in the densest environments of the interstellar medium. These are giant molecular clouds,” said Loeb, confirming that these environments are both too far away and are not conducive to the development of hydrogen icebergs.

The hydrogen iceberg theory was for many reasons very very speculative, and not very convincing, which is why I never posted a link to it when it became clickbait for the mainstream press several months ago. The object’s behavior as it zipped through the solar system, combined with its elongated shape, still leave us with questions. While some scientists have definitely stated it could not have been an alien spacecraft, that likely conclusion remains as uncertain as the theory that it was a hydrogen iceberg.

The only way we will definitely know is to go and look at it. And such a mission remains possible, with launch dates in 2021, 2022, or 2023, with technology we presently have, if we were to move fast.

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Corroded Martian southern highlands

2:05 pm

Corroded Martian terrain in the southern highlands
Click for full image.

Today’s cool image is another example of strange terrain on Mars that is difficult to explain, though one can make some guesses. The photo to the right, rotated, cropped, and reduced to post here, was taken on May 29, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows an area in a region dubbed Aonia and located in the southern cratered highlands directly south of Valles Marineris.

This spot is in the high mid-latitudes, 55 degrees south. In the northern lowland plains one would expect to see a lot of evidence of ice, either as debris covered glaciers in craters or flowing off of mesas, or in an underground ice table that is revealed from impacts and other events that caused it to melt temporarily in the past for a brief instant.

No such features are apparent in this image however. In fact, the photo seems to show a very dry place, with the surface almost all hard bedrock that has been eroded to leave behind rough and sharp features. That a significant amount of erosion has occurred here is indicated by the pedestal crater near the image’s top. When its impact took place the topography was higher. Since then the ground around this crater has been worn away, with the mashed material under the impact at a higher density and more resistant to erosion.

If this spot has an ice table or any buried glacial material, it is not obvious, and certainly not revealed by this erosion.

The two square boxes indicate two insets that I have only cropped to show them at full resolution, and are posted below.
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Catastrophes on Mars and Earth

1:32 pm

Big rock break in Kasei Valles
Click for full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on May 13, 2020, and shows what appears to be a giant block that at some point was attached to the cliff, and then broke off and fell away to the north. Subsequent erosion over the later eons widened the break until it now looks like a canyon.

Sounds great, but the event that separated this big piece of mountain, almost a mile across, from its cliffside was possibly even more catastrophic. And it might not have involved a sudden break and fall, but something more spectacular, and also still impossible based on everything we know about Mars.

Uncovering what really happened at this spot on Mars will not only help us understand the geological history of the Red Planet, it could also amazingly enough help illustrate the cultural shifts going on right now on Earth, and how to shift them in a more rational and sane direction.

This image is located near the outlet of Kasei Valles, one of the larger valleys draining downward from the Tharsis Bulge where Mars’ giant volcanoes are located. The overview map below shows us what Kasei Valles looks like in this area.
» Read more

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Engineers recharge Ingenuity’s batteries on its way to Mars

9:39 am

Engineers have successfully completed their first in-flight maintenance recharge of the batteries on Perseverance’s small test helicopter Ingenuity.

NASA’s Ingenuity Mars Helicopter received a checkout and recharge of its power system on Friday, Aug. 7, one week into its near seven-month journey to Mars with the Perseverance rover. This marks the first time the helicopter has been powered up and its batteries have been charged in the space environment.

During the eight-hour operation, the performance of the rotorcraft’s six lithium-ion batteries was analyzed as the team brought their charge level up to 35%. The project has determined a low charge state is optimal for battery health during the cruise to Mars.

They plan to do these partial recharges about once every two weeks during the trip to Mars to keep the battery charged the optimal amount.

About a month after Perseverance has landed in February 2020, it will find a large flat area to deploy Ingenuity, then move away. The helicopter will then begin a 30 day test program to see if it will be able to fly in the very thin Martian atmosphere, only about 1% as thick as Earth’s.

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Giant impact covered almost half of Gandymede’s surface

9:31 am

Artist's illustration of Ganydmede
Click for full illustration.

The uncertainty of science: Computer modeling and a review of images taken by Voyager 1 and 2 and the Galileo orbiter of Jupiter’s moon Ganymede now suggest the existence of a giant impact so large that it covers almost half the moon’s surface.

The artist’s illustration of Ganymede on the right, based on our presently incomplete set of global images, shows this impact area as the circular dark region.

Many furrows, or trough formations, have been observed on the surface of Ganymede, one of the Jovian moons. This research group comprehensively reanalyzed image data of Ganymede obtained by NASA’s Voyager 1, Voyager 2, and Galileo spacecrafts. The results revealed that almost all of these furrows appear to be arranged in concentric rings centered around a single point, indicating that this global multiring structure may be the remains of a giant crater. The radial extent of the multiring structures measured along Ganymede’s surface is 7800 km. For comparison, the mean circumference of Ganymede is only 16,530 km. If correct, this is the largest crater yet identified in the Solar System. The previous record holder with a 1900 km radius is on Calisto, another Jovian moon.

The conclusion reached here is very uncertain, since we really do not have a high resolution global map of Ganymede. All three spacecraft were only able to send back a scattering of high resolution images. The global map is based on Earth observations and images from the Hubble Space Telescope.

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Betelgeuse dimming caused by outburst

9:08 am

The uncertainty of science: According to new data from the Hubble Space Telescope, astronomers are now proposing that the dimming seen earlier this year in the red giant Betelgeuse was caused not by a known variation cycle or by a large starspot moving across its surface, but by an large outburst of material, thrown out from the star.

Ultraviolet observations by the Hubble Space Telescope suggest that the unexpected dimming was probably caused by an immense amount of superhot material ejected into space. The material cooled and formed a dust cloud that blocked the starlight coming from about a quarter of Betelgeuse’s surface.

That we now have three creditable but different theories, all based on evidence, for explaining the dimming that occurred from October 2019 to April 2020 suggests that we really still have no idea what specifically caused it. All three theories however are based on what we do know about Betelgeuse, that it is giant blobby gasbag that has dark starspots on its surface, that has giant convection cells that bubble up from below and release material periodically, and that it pulses in a variety of cycles predictably over time.

It could be any of these phenomenon that caused last year’s dimming, or even a combination of two or more. The information available so far is just too sketchy to pin this down more precisely.

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OSIRIS-REx completes closest sample grab rehearsal

8:45 am

OSIRIS-REx yesterday successfully completed its closest sample grab rehearsal, bringing the spacecraft about 131 feet from the surface of the asteroid Bennu.

The approximately four-hour “Matchpoint” rehearsal took the spacecraft through the first three of the sampling sequence’s four maneuvers: the orbit departure burn, the “Checkpoint” burn and the Matchpoint burn. Checkpoint is the point where the spacecraft autonomously checks its position and velocity before adjusting its trajectory down toward the event’s third maneuver. Matchpoint is the moment when the spacecraft matches Bennu’s rotation in order to fly in tandem with the asteroid surface, directly above the sample site, before touching down on the targeted spot.

Four hours after departing its 0.6-mile (1-km) safe-home orbit, OSIRIS-REx performed the Checkpoint maneuver at an approximate altitude of 410 feet (125 meters) above Bennu’s surface. From there, the spacecraft continued to descend for another eight minutes to perform the Matchpoint burn. After descending on this new trajectory for another three minutes, the spacecraft reached an altitude of approximately 131 ft (40 m) – the closest the spacecraft has ever been to Bennu – and then performed a back-away burn to complete the rehearsal.

During the rehearsal, the spacecraft successfully deployed its sampling arm, the Touch-And-Go Sample Acquisition Mechanism (TAGSAM), from its folded, parked position out to the sample collection configuration. Additionally, some of the spacecraft’s instruments collected science and navigation images and made spectrometry observations of the sample site, as will occur during the sample collection event. These images and science data were downlinked to Earth after the event’s conclusion.

The actual sample-grab-and-go attempt is scheduled for October 20th.

The short video below the fold shows spacecraft as it makes its closest approach. From the youtube page:
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Martian sand traps and elongated dunes

9:14 am

Elongated dunes on Mars
Click for full image.

Cool image time! The photo to the left, rotated, cropped, and reduced to post here, was taken on June 23, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). I was attracted by the uncaptioned image’s title, “Elongating Linear Dunes at Meroe Patera.” What are elongating linear dunes?

The photo shows two such dunes, stretching out to the southwest away from the pile of sand that abuts the cliff to the northwest. Unlike most dunes, which usually form and travel in groups, these for some reason form single straight lines extending for some distance.

I contacted the scientist who requested this image, Joel Davis of the Natural History Museum in London, hoping he could answer some questions about these strangely shaped dunes, and discovered that he was studying this exact subject for a paper since published. As noted in the paper’s introduction,
» Read more

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Snapped cable damages Arecibo radio telescope

12:25 pm

One of the cables that supports the central platform above the Arecibo Observatory’s giant dish snapped yesterday, damaging the dish and shutting down operations.

The break occurred about 2:45 a.m. When the three-inch cable fell it also damaged about 6-8 panels in the Gregorian Dome and twisted the platform used to access the dome. It is not yet clear what caused the cable to break. “We have a team of experts assessing the situation,” says Francisco Cordova, the director of the observatory. “Our focus is assuring the safety of our staff, protecting the facilities and equipment, and restoring the facility to full operations as soon as possible, so it can continue to assist scientists around the world.”

The radio telescope has not much luck the past few years. It was badly damaged and shut down for a long time after Hurricane Maria in 2017, with repairs from that still on-going.

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The edge of Mars’ south polar layered cap

12:10 pm

The edge of the Martian south pole layered deposits
Click for full image.

Cool image time! The photo to the right, rotated and cropped to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on April 10, 2020, and shows the edge of what scientists have dubbed Mars’s south polar layered deposits. The high point, towards the south, is at the bottom, and the terraced layers descend downward to the plains as you move up the image, to the north.

In essence, this spot is the edge of the southern ice cap, though unlike the north polar ice cap, this edge is not the edge of the visible ice cap, but the edge of a much larger field of layered deposits of mixed dust and ice. In the north the ice cap almost entirely covers these layered deposits. In the south the residual ice cap does not. Instead, the layered deposits extend out far beyond the smaller residual ice cap.

The map below provides the geography of the south pole, with the location of this image indicated by the blue cross.
» Read more

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TESS completes primary mission

9:33 am

Having now imaged 75% of the entire night sky and completing its primary mission, scientists have now begun the extended mission for the Transiting Exoplanet Survey Satellite (TESS), designed to look for transiting exoplanets.

TESS monitors 24-by-96-degree strips of the sky called sectors for about a month using its four cameras. The mission spent its first year observing 13 sectors comprising the southern sky and then spent another year imaging the northern sky.

Now in its extended mission, TESS has turned around to resume surveying the south. In addition, the TESS team has introduced improvements to the way the satellite collects and processes data. Its cameras now capture a full image every 10 minutes, three times faster than during the primary mission. A new fast mode allows the brightness of thousands of stars to be measured every 20 seconds, along with the previous method of collecting these observations from tens of thousands of stars every two minutes. The faster measurements will allow TESS to better resolve brightness changes caused by stellar oscillations and to capture explosive flares from active stars in greater detail.

These changes will remain in place for the duration of the extended mission, which will be completed in September 2022. After spending a year imaging the southern sky, TESS will take another 15 months to collect additional observations in the north and to survey areas along the ecliptic – the plane of Earth’s orbit around the Sun – that the satellite has not yet imaged.

So far the telescope has spotted more than 2,100 exoplanet candidates, with 66 confirmed.

All told, TESS has divided the sky into 26 sectors, 13 in the north and 13 in the south. It can only look at one at a time for a month, and scientists use that one month data, collected more than once, to see if there are any changes. Because of the gaps in TESS’s view of each sector, however, it is guaranteed to miss some exoplanets (the majority) whose transits occur when it is not looking.

Imagine if we had 25 more of these space telescopes in orbit, so that each sector could be watched continually. This is totally doable now, and would make it possible to soon create a census of transiting exoplanets across the entire sky.

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Cryovolcanism on Ceres still ongoing?

10:02 am

3D simulation of Occator Crater on Ceres
Click for full 3D simulation image.
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According to a new detailed analysis of data from the Dawn mission, scientists are now postulating that cryovolcanism in Occator Crater on Ceres began immediately after impact about 22 million years ago and has continued in fits and starts since.

Occator Crater was formed about 22 million years ago by a large impact. As in many other impact craters on Earth and on other planets, a central peak was formed, which collapsed again after some time. About 7.5 million years ago, brine rose to the surface within the remnants of the central peak. The water evaporated and certain salts, so-called carbonates, remained. They are responsible for the prominent bright deposits we see today, called Cerealia Facula, in the center of Occator Crater. Due to the loss of material in the interior, the inner part of the crater subsided. A round depression with a diameter of about 15 kilometers formed.

In the following millions of years, activity concentrated mainly on the eastern part of the crater floor. Through cracks and furrows, brine also rose to the surface there and produced further bright deposits, the Vinalia Faculae. About 2 million years ago the center of the crater woke up again: brine rose to the surface and within the central depression a dome of bright material was formed. “This process continued up to a million years ago and maybe even until today,” Dr. Nico Schmedemann from the University of Münster summarizes.

This hypothesis is further supported by second paper that proposes there remains a reservoir of salty underground liquid water in the tiny planet’s interior. Both add weight to the idea that any object in space that is large enough for gravity to force it into a spherical shape is going to behave like a planet, with a complex and active geology.

The first paper has a lot of uncertainty, however, centering entirely on its dependence on crater counts to determine age. While providing a rough age estimate, the method depends on many assumptions, is indirect, and could easily be entirely wrong.

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Ascraeus Mons, Mars’ second highest mountain

3:06 pm

Ascraeus Mons

Today’s cool Mars’ image started out when I came across an interesting image of a depression on the northern flank of the giant Martian volcano Ascraeus Mons, the northernmost of the line of three giant volcanoes just to the east of the biggest of all, Olympus Mons.

To provide context I created an overview showing the entire volcano (with the white rectangle showing the location of the depression image), and suddenly realized that this overview might actually be more interesting to my readers. To the right is that overview of Ascreaus, with a scale across the bottom to indicate the elevation of the mountain above what scientists have determined to be Mars’ pseudo sea level.

Notice that this volcano, the second highest on Mars, rises more than 43,000 feet above the surrounding plains. Its peak is estimated to be about 59,000 feet high, making it taller than Mt. Everest by about 30,000 feet (more than twice its height). Its diameter is approximately 300 miles across, giving it a much steeper profile than the higher but more spread out Olympus Mons. The map below shows this mountain in relation to Olympus as well as its nearby partner volcanoes.
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Hayabusa-2’s future asteroid targets

10:02 am

Link here. There are two prime candidate asteroid targets, both near Earth astroids.

The possible secondary targets include the oblong asteroid 2001 AV43 or the asteroid 1998 KY 26. They’re each about the size of a large house and both orbit the Sun in roughly 500 days. The proposed plan would see Hayabusa 2 arriving at 2001 AV43 in the late 2029 time frame, or reaching 1998 KY 26 in July 2031. Both asteroids have a low enough relative speed relative to the spacecraft to put them within (eventual) reach after Hayabusa 2’s December flyby.

Interestingly, 2001 AV43 will fly 313,000 km from Earth (0.8 times the Earth-Moon distance) on November 11, 2029.

The two asteroids were selected from an initial field of 354 candidates, which was winnowed down based on accessibility and scientific interest. Both are fast rotators, as evidenced by their light curves, each spinning on its respective axis once every 10 minutes. This represents the shortest “day” of any known object in the solar system, suggesting that these asteroids are in fact solid objects and not simply loosely aggregated “rubble piles.” A visit to one of these asteroids would mark the first time a space mission has seen such an enigmatic fast rotator up close.

The asteroid 1998 KY26 is also a possible carbonaceous (C-type) asteroid, and Hayabusa 2’s exploration of such a space rock would be another first.

Going to 1998 KY26 would also require a distant pass of another asteroid. Going to 2001 AV43 would require a fly-by of Venus, which could provide more data on that planet. Based on this information, my guess is that they will opt for 1998 KY26.

The decision must likely be made before Hayabusa-2 drops off its Ryugu samples to Earth on December 6, 2020.

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OSIRIS-REx preps for final rehearsal of sample grab

9:40 am

The OSIRIS-REx science and engineering team is getting ready for its August 11th final rehearsal of the sample grab-and-go at the asteroid Bennu that it plans to do in October.

If the rehearsal goes right, the spacecraft will descend to within 131 feet of the surface of Bennu as it deploys its equipment as if it would continue down to the surface. It will also fly in formation above the Nightingale sample site when it does this, taking the highest resolution images yet of the surface of the asteroid.

It will then back off, returning to its home orbit farther from Bennu. Engineers will then review what happened, and use that data to prepare for the actual sample grab-and-go, set for October 20, 2020.

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