Tag: science

Dried mud cracks on Mars?

3:10 pm

Mud cracks on Mars?

Cool image time! The image to the right, cropped and rotated to post here, was one of the uncaptioned photographs in the December Mars Reconnaissance Orbiter (MRO) image release. If you click on the image you can see the entire photograph. I have cropped the most interesting area, though cracks can be seen in other areas in the image.

What we appear to have here is a darker lower valley filled with dried mud, which over time has cracked as it dried. At its edges there appear to be ripples, almost like one sees on the beach as waves wash the shore. The perimeter slopes even show darker streaks as if the water in some places lapped up the slopes, and in others flowed downward into the valley.

Later, several meteorite impacts occurred, the largest of which produced concentric dried cracks on its outside perimeter. This impact also provides a rough idea of the depth of the mud in this valley.

Mud of course suggests that this lower valley once was filled with water. Was it? It is not possible now to come to a firm conclusion, but this image’s location shown by the red dot in the overview map below and to the right, provides a clue that strengthens this hypothesis.
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OSIRIS-REx flies over Bennu’s north pole

10:09 am

Bennu's north pole

Cool movie time! OSIRIS-REx has completed its first planned fly-over of Bennu, this time above its north pole, and the science team has released a short movie showing part of that fly-over. I have embedded the movie below the fold.

This series of MapCam images was taken over the course of about four hours and 19 minutes on Dec. 4, 2018, as OSIRIS-REx made its first pass over Bennu’s north pole. The images were captured as the spacecraft was inbound toward Bennu, shortly before its closest approach of the asteroid’s pole. As the asteroid rotates and grows larger in the field of view, the range to the center of Bennu shrinks from about 7.1 to 5.8 miles (11.4 to 9.3 km).

They have four more fly-overs of the asteroid’s poles and equator as they assemble a detailed map of its surface.
» Read more

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New asteroid radar images

12:59 pm

near-Earth asteroid 2003 SD220

Cool radar images! The set of radar images above of near-Earth asteroid 2003 SD220 were created by combining radar data from three different radar telescopes on Earth, Arecibo in Puerto Rico, Green Bank in West Virginia, and Goldstone in California. As the press release notes:

The asteroid will fly safely past Earth on Saturday, Dec. 22, at a distance of about 1.8 million miles (2.9 million kilometers). This will be the asteroid’s closest approach in more than 400 years and the closest until 2070, when the asteroid will safely approach Earth slightly closer.

The radar images reveal an asteroid with a length of at least one mile (1.6 kilometers) and a shape similar to that of the exposed portion of a hippopotamus wading in a river.

The images have a resolution of 12 feet per pixel, so a close look should be able to reveal any large boulders, should they exist. Instead, I see a soft surface that to me resembles the surface of a sand dune, floating unattached to anything in space.

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No rotational light curve from Ultima Thule?

8:55 pm

Data from New Horizons as it is quickly approaching Ultima Thule has found that even though the object is expected to be oblong or even two objects it has shown absolutely no variation in light as it rotates.

Even though scientists determined in 2017 that the Kuiper Belt object isn’t shaped like a sphere – that it is probably elongated or maybe even two objects – they haven’t seen the repeated pulsations in brightness that they’d expect from a rotating object of that shape. The periodic variation in brightness during every rotation produces what scientists refer to as a light curve.

“It’s really a puzzle,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute. “I call this Ultima’s first puzzle – why does it have such a tiny light curve that we can’t even detect it? I expect the detailed flyby images coming soon to give us many more mysteries, but I did not expect this, and so soon.”

They have several theories, all implausible, to explain this. It could be they are looking at the object’s pole. Or maybe a dust cloud or numerous tumbling moons surround the object and hide the light variation.

Fortunately, we shall have an answer to this mystery in less than two weeks, when New Horizons zips past.

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InSight installs seismometer on Martian surface

8:39 am

InSight has successfully placed its first instrument, its seismometer, on Martian surface.

They aren’t yet ready to start gathering data, however.

In the coming days, the InSight team will work on leveling the seismometer, which is sitting on ground that is tilted 2 to 3 degrees. The first seismometer science data should begin to flow back to Earth after the seismometer is in the right position.

But engineers and scientists at JPL, the French national space agency Centre National d’Études Spatiales (CNES) and other institutions affiliated with the SEIS team will need several additional weeks to make sure the returned data are as clear as possible. For one thing, they will check and possibly adjust the seismometer’s long, wire-lined tether to minimize noise that could travel along it to the seismometer. Then, in early January, engineers expect to command the robotic arm to place the Wind and Thermal Shield over the seismometer to stabilize the environment around the sensors.

They plan on deploying the heat probe (which will drill down about 16 feet) in January.

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Curiosity’s future travels

2:11 pm

MRO image of Curiosity's future travels

In the December release of images from the high resolution camera on Mars Reconnaissance Orbiter (MRO), there was one image entitled “Monitor Region Near Curiosity Rover.” To the right is a reduced, cropped, and rotated section of that image, annotated by me to show Curiosity’s future planned route (indicated by the yellow line). If you click on the image you can see the untouched full resolution version.

Curiosity’s journey has not yet brought it onto the terrain shown in this image. (For the overall context of Curiosity’s travels, see Pinpointing Curiosity’s location in Gale Crater.) The rover is right now just off the left edge of the photograph, on the white ridge dubbed Vera Rubin Ridge visible in the uppermost left. This week it completed the last planned drill sampling on that ridge, and it will soon descend off the ridge and begin heading along the yellow route up the mountain. The white dots along its future route are the locations of recurring slope lines, believed to be seasonal seeps of brine coming from below and causing gentle landslides that darken the surface. As you can see, they hope to get very close to the first seep, and will observe the second from across the canyon from a distance of about 1,200 feet.

The peak of Mount Sharp is quite a distance to the south, far beyond the bottom of the photograph. Even in these proposed travels the rover will remain in the mountain’s lowest foothills, though the terrain will be getting considerably more dramatic.

Below is a full resolution section of the image showing the spectacular canyon to the south of that second seep. This is where Curiosity will be going, a deep canyon about 1,500 feet across and probably as deep, its floor a smooth series of curved layers, reminiscent of The Wave in northern Arizona. The canyon appears to show evidence of water flow down its slopes, but that is unproven.
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BepiColombo begins first operational engine burn

9:09 am

The European/Japanese mission to Mercury has begun the first operational firing of its four ion engines, set to last for the next two months.

This might seem like a ridiculously long burn, since most conventional rocket engines fire for minutes, not months. These are ion engines, however, far more efficient but producing a very tiny acceleration. It takes a long time for their burns to accumulate a velocity change.

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Comparing Ryugu and Bennu

9:30 am

Link here. As much as they are alike, which is not surprising as they both come from the same asteroid family, the article notes the surprising differences.



Both asteroids are also liberally strewn with boulders – a challenge to mission planners on each team, who hope to descend close enough to scoop up samples for return to Earth. “It’s certainly more rugged than we had expected,” Lauretta says. 

But while boulders on Ryugu look to be unpleasantly ubiquitous, Bennu’s terrain is more varied, with more-obvious places where a safe touchdown might be possible. And, Lauretta notes, the OSIRIS-REx spacecraft is only recently arrived.

“We have a long time to explore and make the crucial decisions about where to go,” he says.

The biggest difference has to do with water. Even though scientists believe them to be portions of the same parent body, which broke apart between 800 million and one billion years ago, Bennu appears to be water rich, while Ryugu is less so. Within a week of arrival, infrared spectrometers on OSIRIS-REx were finding evidence of water-bearing minerals, and not just in localised patches. “We saw this in every single one of the spectra we have taken to date,” says Amy Simon, of NASA’s Goddard Space Flight Centre in Greenbelt, Maryland. 

One of the reasons Bennu was chosen as OSIRIS-REx’s target, Lauretta says, was the hope it would be rich in water, and possibly in organic compounds.

The similarities and differences in the samples both spacecraft will bring back will be most revealing.

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New Horizons sees no hazards, will do closest fly-by of Ultima Thule

9:04 am

After three weeks of intense observations and seeing no significant objects orbiting close to the Kuiper Belt object Ultima Thule, the New Horizons team has decided to go for the closest fly-by on January 1, 2019.

After almost three weeks of sensitive searches for rings, small moons and other potential hazards around the object, New Horizons Principal Investigator Alan Stern gave the “all clear” for the spacecraft to remain on a path that takes it about 2,200 miles (3,500 kilometers) from Ultima, instead of a hazard-avoiding detour that would have pushed it three times farther out. With New Horizons blazing though space at some 31,500 miles (50,700 kilometers) per hour, a particle as small as a grain of rice could be lethal to the piano-sized probe.

We should begin to see more detailed images soon. Because of the speed in which New Horizons is traveling, it will not get very close until it is almost on top of Ultima Thule, so the best images will all occur over a very short span of time.

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Saturn’s rings are dying

8:56 am

Using new ground-based observations, scientists now predict that Saturn’s rings are dying at the fastest predicted rate, and will disappear within 300 million years, at the most.

Dr Tom Stallard, Associate Professor in Planetary Astronomy at the University of Leicester and Dr James O’Donoghue, who studied for his PhD at the University of Leicester, have found that Saturn’s rings are dying at the maximum rate estimated from Voyager 1 and 2 observations made decades ago.

The rings of ice are being pulled into Saturn by gravity as particles of ice under the influence of Saturn’s magnetic field. Dr O’Donoghue, who now works at NASA’s Goddard Space Flight Center in Greenbelt, Maryland said: “We estimate that this ‘ring rain’ drains the equivalent of an Olympic-sized swimming pool from Saturn’s rings in half an hour. The entire ring system will be gone in 300 million years.”

Dr O’Donoghue believes that the rings could even disappear quicker than this. “Add to this the Cassini-spacecraft detected ring-material falling into Saturn’s equator, and the rings have less than 100 million years to live.”

Over the decades I have read numerous papers by scientists saying that rings this bright and large must be a relatively short-lived event, and that we are lucky to have seen them. This research only reinforces this conclusion.

At the same time, we do not yet know the frequency or the cause of the events that give rise such bright rings. It could be that such rings are short-lived, but happen frequently enough that it is still not rare to see them in any solar system. And we won’t know this until we get a more complete census of many solar systems, seen up-close.

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Astronomers discover most distant solar system object so far

9:17 am

Worlds without end: Astronomers have discovered a dwarf planet about 300 miles in diameter orbiting the Sun at a distance of 120 astronomical units, making it the most distant solar system object discovered so far.

“2018 VG18 is much more distant and slower moving than any other observed Solar System object, so it will take a few years to fully determine its orbit,” said Sheppard. “But it was found in a similar location on the sky to the other known extreme Solar System objects, suggesting it might have the same type of orbit that most of them do. The orbital similarities shown by many of the known small, distant Solar System bodies was the catalyst for our original assertion that there is a distant, massive planet at several hundred AU shepherding these smaller objects.”

“All that we currently know about 2018 VG18 is its extreme distance from the Sun, its approximate diameter, and its color,” added Tholen “Because 2018 VG18 is so distant, it orbits very slowly, likely taking more than 1,000 years to take one trip around the Sun.”

I guarantee there are more of these discoveries to come. Many more.

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Two dead at U.S. Antarctic station

1:12 pm

An accident of some kind has apparently killed two individuals at the U.S. McMurdo station in Antarctica yesterday.

The National Science Foundation says two technicians working on a fire-suppression system at an Antarctica scientific station were found unconscious and died.

The foundation said Wednesday the two had been working in a building at McMurdo Station, which is on Ross Island. It says they were found on the floor by a helicopter pilot who had landed after spotting what appeared to be smoke from the building.

Nothing more is as yet known.

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Trace Gas Orbiter finds no methane on Mars

11:31 am

The uncertainty of science: Europe’s Trace Gas Orbiter (TGO) has failed to detect any methane in Mars’ atmosphere, even though data from Mars Express in 2004 had said it should see some.

The Mars Express orbiter first detected hints of methane in the martian atmosphere in 2004. But some scientists said the orbiter’s instruments that found it—at a level of 10 parts per billion (ppb)—weren’t sensitive enough to produce reliable results. Ten years later, NASA’s Curiosity rover detected a methane spike of 7 ppb from its base in Gale crater, which lasted several months. Several years later, Curiosity’s scientists then discovered a minute seasonal cycle, with methane levels peaking at 0.7 ppb in the late northern summer.

To settle this mystery, the European Space Agency’s Trace Gas Orbiter (TGO), which arrived at Mars in 2016, this year began to scan the atmosphere for methane. Two of the TGO’s spectrometers—a Belgian instrument called NOMAD and a Russian one called ACS—were designed to detect methane in such low concentrations that researchers were sure they would. Both instruments, which analyze horizontal slices of the martian atmosphere backlit by the sun, are working well, scientists on the team said today at a semiannual meeting of the American Geophysical Union in Washington, D.C. There’s still some noise to clean up, said Ann Carine Vandaele, NOMAD’s principal investigator and a planetary scientist at the Royal Belgian Institute for Space Aeronomy in Brussels, in her talk. “But we already know we can’t see any methane.”

The team’s initial results show no detection of methane down to a minute level of 50 parts per trillion, with their observations going down nearly all the way to the martian surface.

The data says that any methane seen on the surface (such as by Curiosity) must be coming from below, not from off world, which in itself is a surprise since the scientists expected some methane to be coming from interplanetary dust. TGO has found none..

There are a lot of uncertainties still, so stay tuned.

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Cats might be larger now than in the past

10:44 am

The uncertainty of science: A careful analysis of cat bones from numerous Viking archeology sites going back 2000 years suggests that the size of cats increased during those centuries.

After carefully measuring the bones with an electronic caliper, Bitz-Thorsen and Gotfredsen compared them with those of modern Danish cats dating from 1870 to the present. On average, domesticated cats grew by about 16% between the Viking Age and today, they report this month in the Danish Journal of Archaeology.

The study only focused on Danish cats, so the findings may not be generalizable to other parts of the world. However, a 1987 study of a collection of cat bones from Germany bolsters the idea that domestic cats of the medieval age were smaller than modern-day pets.

They think the size increase was due to better food.

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R.I.P. Riccardo Giacconi

10:13 am

The astronomy community is mourning the passing of Riccardo Giacconi, a pioneer in space X-ray astronomy as well as the first director of the Space Telescope Science Institute, which operates Hubble.

What made him an especially interesting man is that he initially strongly opposed Hubble, preferring the money be spent on X-ray space telescopes. When, during the writing of The Universe in a Mirror, I asked him what prompted his change of opinion that made him head of Hubble, he explained that he felt he “wasn’t being used.” The money for X-ray astronomy just wasn’t there, and rather than chase rainbows he decided to hitch his wagon to something that was certain to produce new science.

The irony is that it was Hubble’s success that probably helped generate the funding for later X-ray space telescopes, such as Chandra.,

Giacconi was a unique and brilliant man. His early X-ray instruments were built by a private commercial company he ran, not a university or NASA. In a sense he was following the classic and older American model here that was abandoned in the 1970s, and is only now beginning to see a resurgence.

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OSIRIS-REx finds evidence of water on Bennu

12:01 am

Bennu from 15 miles

One of OSIRIS-REx’s instruments has now found evidence of water on the rubble-pile asteroid Bennu.

Recently analyzed data from NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) mission has revealed water locked inside the clays that make up its scientific target, the asteroid Bennu.

During the mission’s approach phase, between mid-August and early December, the spacecraft traveled 1.4 million miles (2.2 million km) on its journey from Earth to arrive at a location 12 miles (19 km) from Bennu on Dec. 3. During this time, the science team on Earth aimed three of the spacecraft’s instruments towards Bennu and began making the mission’s first scientific observations of the asteroid. OSIRIS-REx is NASA’s first asteroid sample return mission.

Data obtained from the spacecraft’s two spectrometers, the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) and the OSIRIS-REx Thermal Emission Spectrometer (OTES), reveal the presence of molecules that contain oxygen and hydrogen atoms bonded together, known as “hydroxyls.” The team suspects that these hydroxyl groups exist globally across the asteroid in water-bearing clay minerals, meaning that at some point, Bennu’s rocky material interacted with water. While Bennu itself is too small to have ever hosted liquid water, the finding does indicate that liquid water was present at some time on Bennu’s parent body, a much larger asteroid.

The image on the right, reduced to show here, was created from 12 images taken on December 2, 2018 from about 15 miles. If you click on the image you can see the full resolution photograph, which is quite incredible. While the asteroid’s shape is approximately what was expected from ground-based observations and computer modeling, the giant boulder on the limb on the bottom right is about four times bigger than expected.

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Voyager 2 enters interstellar space

11:34 am

The Voyager 2 spacecraft, launched in 1977, has entered interstellar space, becoming the second human spacecraft to achieve this.

Comparing data from different instruments aboard the trailblazing spacecraft, mission scientists determined the probe crossed the outer edge of the heliosphere on Nov. 5. This boundary, called the heliopause, is where the tenuous, hot solar wind meets the cold, dense interstellar medium. Its twin, Voyager 1, crossed this boundary in 2012, but Voyager 2 carries a working instrument that will provide first-of-its-kind observations of the nature of this gateway into interstellar space.

Voyager 2 now is slightly more than 11 billion miles (18 billion kilometers) from Earth. Mission operators still can communicate with Voyager 2 as it enters this new phase of its journey, but information – moving at the speed of light – takes about 16.5 hours to travel from the spacecraft to Earth. By comparison, light traveling from the Sun takes about eight minutes to reach Earth.

When I first wrote about these spacecraft in the 1990s, it was thought that Voyager 2 would probably not exit the solar system until the 2020s, meaning that its nuclear power source might die before that happened. That it has happened now, so much earlier, helps map the size of the heliosphere as well as the pressure that might be placed upon it by the interstellar medium

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New Horizons completes another course correction before flyby

11:53 pm

On December 2 New Horizons successfully completed another engine burn to refine its course for its January 1, 2019 flyby of the Kuiper Belt object Ultima Thule.

The maneuver was designed to keep New Horizons on track toward its ideal arrival time and closest distance to Ultima, just 2,200 miles (3,500 kilometers) at 12:33 a.m. EST on Jan. 1. At the time of the burn New Horizons was 4.03 billon miles (6.48 billion kilometers) from Earth and just 40 million miles (64 million kilometers) from Ultima – less than half the distance between Earth and the Sun. From that far away, the radio signals carrying data from the spacecraft needed six hours, at light speed, to reach home.

The team is analyzing whether to conduct up to three other course-correction maneuvers to home in on Ultima Thule.

The distance to Ultima Thule is still too much to produce detailed images. New Horizons however is going very fast, so in the coming three weeks this will change drastically, and for the better.

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InSight tests its robot arm

11:42 pm

InSight has unfolded its robot arm and is beginning to use it to photograph the surrounding area to figure out where to place the spacecraft’s ground-sensing instruments.

With a reach of nearly 6 feet (2 meters), the arm will be used to pick up science instruments from the lander’s deck, gently setting them on the Martian surface at Elysium Planitia, the lava plain where InSight touched down on Nov. 26.

But first, the arm will use its Instrument Deployment Camera, located on its elbow, to take photos of the terrain in front of the lander. These images will help mission team members determine where to set InSight’s seismometer and heat flow probe – the only instruments ever to be robotically placed on the surface of another planet.

They are proceeding carefully, so actually deployment might not occur for several months, just make everything goes well.

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Sunspot update November 2018: Minimum continues

11:26 am

NOAA’s monthly update of the solar cycle, covering sunspot activity for November 2018, was released yesterday. As I have done every month since this website began in July 2011, I am posting it below, annotated to give it some context.

November 2018 sunspot activity

The graph above has been modified to show the predictions of the solar science community. The green curves show the community’s two original predictions from April 2007, with half the scientists predicting a very strong maximum and half predicting a weak one. The red curve is their revised May 2009 prediction.

As I have been expecting now for the last three months, NOAA has finally revised this graph to extend it past the end of 2018. The graph below is the graph from October, which follows the layout and design used since 2007. You can see the differences by comparing the two graphs. In extending the new graph to the end of 2022, they fortunately did not change the design significantly. However, because the new graph has a slightly different scale, I have stretched the green and red curves to make them fit properly. While I suspect the poor quality of the 2007 and 2009 predictions is one reason they do not include them on their graph, I think it essential to add them to better understand the limitations of the science.
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BepiColombo tests its ion engines

8:22 am

The joint European/Japanese mission BepiColombo has begun testing its ion engine thrusters for the first time in space as it heads to Mercury.

Testing took place during a unique window, in which BepiColombo remained in continuous view of ground-based antennas and communications between the spacecraft and those controlling it could be constantly maintained. This was the only chance to check in detail the functioning of this fundamental part of the spacecraft, as when routine firing begins in mid-December, the position of the spacecraft will mean its antennas will not be pointing at Earth, making it less visible to operators at mission control.

They have so far successfully tested two of the four engines.

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Solar scientists: sunspot increase in next solar cycle

7:47 am

The uncertainty of science: Using new computer models, two solar scientists are now predicting that the next solar cycle will begin in about a year and will see an increase in sunspot activity, compared to the weak cycle just ending.

Their ensemble forecast surprisingly suggests it could even be stronger than the cycle which is just ending. They expect the next cycle to start rising in about a year following the end of the current sunspot cycle minimum and peak in 2024. Bhowmik and Nandi predict space environmental conditions over the next decade would be similar or slightly harsher compared to the last decade. They find no evidence of an impending disappearance of sunspot cycles and thus conclude that speculations of an imminent Sun-induced cooling of global climate is very unlikely.

Their conclusion is different than other predictions that are claiming a weak next cycle, or even the beginning of a grand minimum, with no suspots at all. Since an real understanding of the sunspot cycle remains elusive, and all these predictions rely on computer models, it is hard to say which will be right. The advantage this particular prediction has is that their model appears able to match what has happened for the past 100 years.

Stay tuned.

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The vast southern highlands of Mars

3:34 pm

Small section of Rocky Highlands

Rocky highlands

Cool image time! This week the Mars Reconnaissance Orbiter (MRO) science team made available its monthly release of new images taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The image above is just a small cropped section from one of those new images, released under the name “Rocky Highlands.” The image on the right is a cropped and reduced section of the full photograph, with the white box indicating the small section above. If you click on either you can see the full resolution uncropped photograph and explore its complex and rough terrain.

What should immediately strike you looking at the small inset section above is the difficulty anyone is going to have traversing this country. There are no flat areas. Every inch seems to be a broken and shattered collection of ridges, pits, craters, or rippled dunes. And the inset above is only a tiny representation of the entire image, all of which shows the same kind of badlands.

This forbidding place is located in the southern highlands of Mars, north of Hellas Basin and south of the transition zone that drops down to the northern lowland plains. The white cross on the map below indicates the image location, with green representing the transition zone, blue the northern plains, and red/orange the southern highlands..
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The basement of Mars

12:15 pm

Hellas Basin ripples

Cool image time! The photo on the right, cropped and reduced to post here, was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on May 2, 2018, and shows some very strange ripples and erosion features in one of the lowest elevation locations on Mars, inside Hellas Basin. If you click on the image you can see the full photograph, at full resolution. There are a lot of strange features here, so make sure you take a look at it. The ripples highlighted in the image are between what appear to be three lower basins, and seem to my eye to be ridges created as liquid ebbed and flowed in the basins, depositing material at the shoreline at repeatedly higher and lower levels.

hellas basin

This particular location is not only in Hellas Basin, but it is also located in the deepest part of Hellas, a curved valley located in the basin’s northwest quadrant, as shown by the darker areas in the overview image to the right. The red boxes are other MRO high resolution images, with the cross indicating where this image is located.

This is the basement of Mars, what could be called its own Death Valley. The difference however is that unlike Death Valley, conditions here could be more amendable to life, as the lower elevation means the atmosphere is thicker. The ripples also suggest that liquid water might have once been here, a supposition supported by other low area images of Hellas Basin, most of which show a flattish dappled surface that to me resembles what one would think a dry seafloor bed would look like. The image in this second link also shows what looks like ghost craters that over time became partly buried, something one would also expect to happen if they were at the bottom of a lake, though this could also happen over time on Mars with wind erosion and the movement of dust.

It is also possible that these features come from lava events, so please take my theorizing here with a great big grain of salt. At the same time, recent results have found evidence of paleo lakes scattered all along the eastern rim of the basin, reinforcing the possibility that these were water filled lakes once as well.

Nonetheless, the ripples in the first image above are truly fascinating, as it is clear that at the highest peaks erosion has ripped those peaks away, leaving behind a hollow shaped by the ripples themselves. These features remind me of some cave features I have seen, where mud gets piled but by water flow, and then is over time covered with a crust of harder calcite flowstone. Later, water then washes out the mud underneath, leaving the curved flowstone blanket hanging in the air.

Here in Hellas Basin it looks like something similar has happened, except that at these peaks the outside crust got broken away, allowing wind to slowly suck out the material underneath, leaving these ripple-shaped pits. Whether it was liquid water or lava that helped create these features, the geology left behind is both beautiful and intriguing. I wonder at the chemical make-up of the crust as well as the materials below. And I especially wonder if there are water sources buried within Hellas Basin.

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OSIRIS-REx at Bennu

10:17 am

OSIRIS-REx has successfully completed its last maneuver engine burn to place it in proximity orbit around the asteroid Bennu.

The link takes you to the live NASA stream, which has been a bit hokey. This event is actually not that visually exciting, a bunch of engineers staring at computer screens awaiting data back from the spacecraft indicating that all has occurred as planned. In fact, some felt a bit staged, though the actual event was really happening.

The OSIRIS-REx team has released relatively little data so far, compared to most NASA missions. There will be a press conference in a week when they say they will release more information. I guess we will have to wait until then.

Update: the live stream has shifted to the docking of the manned Soyuz capsule at ISS, which is in itself a more riveting event than OSIRIS-REx’s last engine burn.

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Four more gravitational wave detections

9:16 am

The uncertainty of science: The scientists running the LIGO gravitational wave detector have announced the detection of four more gravitational waves, bringing to eleven the total number so far observed.

During the first observing run O1, from September 12, 2015 to January 19, 2016, gravitational waves from three BBH mergers were detected. The second observing run, which lasted from November 30, 2016, to August 25, 2017, yielded a binary neutron star merger and seven additional binary black hole mergers, including the four new gravitational wave events being reported now. The new events are known as GW170729, GW170809, GW170818 and GW170823 based on the dates on which they were detected. With the detection of four additional BBH mergers the scientists learn more about the population of these binary systems in the universe and about the event rate for these types of coalescences.

The observed BBHs span a wide range of component masses, from 7.6 to 50.6 solar masses. The new event GW170729 is the most massive and distant gravitational-wave source ever observed. In this coalescence, which happened roughly 5 billion years ago, an equivalent energy of almost five solar masses was converted into gravitational radiation.

In two BBHs (GW151226 and GW170729) it is very likely that at least one of the merging black holes is spinning. One of the new events, GW170818, detected by the LIGO and Virgo observatories, was very precisely pinpointed in the sky. It is the best localized BBH to date: its position has been identified with a precision of 39 square degrees (195 times the apparent size of the full moon) in the northern celestial hemisphere. [emphasis mine]

The highlighted quote above illustrates the amount of uncertainty here. Though these appear to be gravitational waves, and have been confirmed in multiple ways, the data is very coarse, providing only a limited amount of basic information about each event. This limited information is still very valuable, and certainly advances our understanding of black holes and their formation, but it is important to recognize the limitations of that data.

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Astronomers get best and earliest view of supernovae ever

9:15 am

Using ground-based telescopes as well as the space telescope Kepler astronomers have obtained their best and earliest view of a Type Ia supernova.

The supernova, named SN 2018oh, was brighter than expected over the first few days. The increased brightness is an indication that it slammed into a nearby companion star. This adds to the growing body of evidence that some, but not all, of these thermonuclear supernovae have a large companion star that triggers the explosion.

Las Cumbres Observatory (LCO), based in Goleta, California, is a global network of 21 robotic telescopes that obtained some of the best data characterizing the supernova in support of the NASA mission. Wenxiong Li, the lead author of one of three papers published today on the finding, was based at LCO when much of the research was underway. Five other LCO astronomers, who are affiliated with the University of California Santa Barbara (UCSB), also contributed to two of the papers.

Understanding the origins of Type Ia supernovae is critical because they are used as standard candles to map out distances in cosmology. They were used to discover Dark Energy, the mysterious force causing the universe to accelerate in its expansion. Astronomers have long known that a supernova is the explosion of a dense white dwarf star (A white dwarf has the mass of the sun, but only the radius of the Earth; one teaspoon of a white dwarf would weigh roughly 23000 pounds) What triggers the explosion is less well understood. One theory holds that the explosions are the merger of two white dwarf stars. Another is that the second star is not a white dwarf at all, but a normal-sized or even giant star that loses only some of its matter to the white dwarf to initiate the explosion. In this theory, the explosion then smashes into the surviving second star, causing the supernova to be exceedingly bright in its early hours.

Finding that Type Ia supernovae can be brighter than previously believed throws a wrench into the results that discovered dark energy, since those results made assumptions about the brightness and thus the distance of those supernovae. If the brightness of these supernovae are not as reliable as expected, they are also less of a standard candle for estimating distance.

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