Tag: asteroids

The never-ending snowstorm circling Saturn

10:21 am

New data suggests that the water being spewed out of Enceladus’s tiger stripes is depositing so much snow and ice on Saturn’s three inner moons, Mimas, Enceladus and Tethys, that these moons, as well as Enceladus, are about twice as bright in radar than previously thought.

Dr Le Gall and a team of researchers from France and the US have analysed 60 radar observations of Saturn’s inner moons, drawing from the full database of observations taken by the Cassini mission between 2004 and 2017. They found that previous reporting on these observations had underestimated the radar brightness by a factor of two.

Unprotected by any atmospheres, Saturn’s inner moons are bombarded by grains of various origins which alter their surface composition and texture. Cassini radar observations can help assess these effects by giving insights into the purity of the satellites’ water ice.

The extreme radar brightness is most likely related to the geysers that pump water from Enceladus’s internal ocean into the region in which the three moons orbit. Ultra-clean water ice particles fall back onto Enceladus itself and precipitate as snow on the other moons’ surfaces.

Dr Le Gall, of LATMOS-UVSQ, Paris, explained: “The super-bright radar signals that we observe require a snow cover that is at least a few tens of centimetres thick. However, the composition alone cannot explain the extremely bright levels recorded. Radar waves can penetrate transparent ice down to few meters and therefore have more opportunities to bounce off buried structures. The sub-surfaces of Saturn’s inner moons must contain highly efficient retro-reflectors that preferentially backscatter radar waves towards their source.”

While the new results suggest that the surfaces of these moons are much brighter that expected, I find the circumstances they describe far more fascinating: a never-ending snow storm in the orbits around Saturn and landing continually on these moons.

My, isn’t the universe wonderful?

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Stony-iron asteroid caused flash on Jupiter in August

11:26 am

According to an analysis of the data obtained from the light flash that occurred when an object hit Jupiter on August 7, scientists have estimated its probably make-up, mass, and size.

They estimate from the energy released by the flash that the impactor could have been an object around 12-16 metres in diameter and with a mass of about 450 tons that disintegrated in the upper atmosphere at an altitude of about 80 kilometres above Jupiter’s clouds. Sankar and Palotai’s models of the light-curve for the flash suggest the impactor had a density typical of stony-iron meteors, indicating that it was a small asteroid rather than a comet.

Their conclusions are strengthened because they were able to compare this flash with five other similar but not as bright flashes, all detected since 2010.

These recent detections, all by amateurs, are because of the higher quality equipment now available to ordinary people, including the use of computers and remote operation. This technology is making it possible for amateurs to discover things that once only professionals could find.

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First high quality image of interstellar comet

2:01 pm

Comet Borisov
Click for full image.

The Gemini Observatory on Mauna Kea has successfully taken the first high resolution image of comet C_2019 Q4, unofficially Comet Borisov (after its discoverer), the first interstellar comet ever discovered.

The image to right, cropped to post here, is that image. It clearly shows the growth of a coma and possible tail, indicating that as it is approaching the Sun it is releasing material from its surface.

Right now the comet is visually very close to the Sun, when looked at from the Earth, making observations difficult. As in the next few months it drops towards its closest approach of the Sun, and the Earth circles around in its own orbit, the viewing angle will improve.

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Interstellar comet discovered?

11:51 pm

An amateur astronomer has discovered what appears right now to be an interstellar comet making its approach into the solar system.

[I]mages show that the incoming object sports a faint but distinct coma and the barest hint of a tail — something ‘Oumuamua lacked — and thus appears to be a comet. Astronomers are no doubt eager to get spectra of the new find to determine what compounds might be escaping from its surface.

Based on current observations, C/2019 Q4’s eccentricity is about 3.2 — definitely hyperbolic. Objects on hyperbolic orbits are unbound to the Sun. They’re most likely to hail from beyond the solar system, flying in from great distances to pay our neighborhood a brief visit before heading off for parts unknown.

If this result holds up, astronomers have an unprecedented opportunity to study a potentially interstellar object in great detail over a long span of time. Based on the comet’s current magnitude (~18) and distance from the Sun (2.7 a.u.), it appears to be a fairly large object — perhaps 10 km or more across, depending on the reflectivity of its surface.

There remains a great deal of uncertainty about comet’s path, which will be better resolved with time and better data.

If it is a comet from beyond the solar system, it will be a spectacular goldmine for scientists, because its coma and tail will allow them to gather a great deal of information about its make-up, far more than they were able to gather about Oumuamua.

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Hayabusa-2 in safe mode for one day on August 29

9:36 am

Japan’s Hayabusa-2 space probe automatically entered safe mode for one day on August 29, causing engineers to postpone a planned operation set for Sept 5.

Hayabusa2 is equipped with four reaction wheels that are used to control the posture of the spacecraft, and posture control is usually performed using three of these reaction wheels. On August 29, the back-up reaction wheel that has not been used since October last year was tested, and an abnormal value (an increased torque) as detected. The spacecraft therefore autonomously moved into the Safe-Hold state. Details of the cause of the abnormal torque value are currently under investigation. On August 30, restoration steps were taken and the spacecraft returned to normal. However, as the spacecraft moved away from the home position due to entering Safe-Hold, we are currently having to return to the home position. We will return to the home position this weekend.

The attitude of the spacecraft is controlled by three reaction wheels as before. Entering the Safe-Hold state is one of the functions employed to keep the spacecraft safe, which means that procedures have worked normally.

In this case it is very clear that this event actually demonstrated that the spacecraft’s systems are operating properly to prevent it from becoming lost. However, the event also underlined the urgency of getting its samples from the asteroid Ryugu back to Earth.

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OSIRIS-REx’s four candidate landing sites

9:07 am

The OSIRIS-REx engineering team has released a short video that flies over in close-up, showing the spacecraft’s four candidate sites on the asteroid Bennu, one of which will be where they will do a touch-and-go sample grab.

They continue to accumulate data on the four sites, all of which pose issues and risks because of nearby boulders and the looseness of Bennu’s rubble pile make-up.

Though all the sites are being considered, my sources in the industry suggest that the two dubbed Sandpiper and Nightingale are being favored. I like Osprey, because it is inside a crater and looks clear, but then, what do I know?

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Arecibo gets $19 million NASA research/education grant

5:25 pm

The Arecibo Observatory in Puerto Rico was today awarded an $19 million NASA research/education grant for studying near Earth asteroids.

NASA awarded the University of Central Florida (which manages the site on behalf of National Science Foundation) the four-year grant to observe and characterize near-Earth objects (NEO) that pose a potential hazard to Earth or that could be candidates for future space missions.

…The award also includes money to support STEM education among high school students in Puerto Rico. The Science, Technology And Research (STAR) Academy brings together 30 local high-school students per semester once a week for 16 classes to learn about science and research at the observatory.

This, plus the recent NSF grant, will keep the telescope operating for at least the next few years.

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Results from tiny MASCOT lander on Ryugu

9:21 pm

The scientists in charge of the tiny MASCOT lander dropped from Japan’s Hayabusa-2 spacecraft today released the results from the lander’s short seventeen hour observations of the surface of Ryugu.

They found that the asteroid has two different types of rocks (why is a mystery) and practically no dust.

Ralf Jaumann and his team were particularly surprised by the lack of dust: “Ryugu’s entire surface is littered with boulders, but we have not discovered dust anywhere. It should be present, due to the bombardment of the asteroid by micrometeorites over billions of years, and their weathering effect. However, as the asteroid has very low gravity – only one-sixtieth of that experienced on Earth’s surface – the dust has either disappeared into cavities on the asteroid or has escaped into space. This gives an indication of the complex geophysical processes occurring on the surface of this small asteroid.”

They also confirmed that the asteroid is a very fragile rubble pile.

“If Ryugu or another similar asteroid were ever to come dangerously close to Earth and an attempt had to be made to divert it, this would need to be done with great care. In the event that it was impacted with great force, the entire asteroid, weighing approximately half-a-billion tonnes, would break up into numerous fragments. Then, many individual parts weighing several tonnes would impact Earth,” says Jaumann, who is supervising the MASCam experiment, interpreting the observations. The asteroid is very similar to carbonaceous meteorites found on Earth, which date back 4.5 billion years. With an average density of just 1.2 grams per cubic centimetre, Ryugu is only a little ‘heavier’ than water ice. But as the asteroid is made up of numerous pieces of rock of different sizes, this means that much of its volume must be traversed by cavities, which probably makes this diamond-shaped body extremely fragile.

MASCOT was another example of a cubesat demonstrating that these tiny spacecraft can do very sophisticated science.

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Japan’s plan for returning Hayabusa-2’s Ryugu samples to Earth

10:07 am

Japan’s today provided an update on what it has done to prepare the location where Hayabusa-2’s samples from the asteroid Ryugu will land on Earth.

The landing site is in the Woomera Prohibited Area (WPA) in the outback of southern Australia. Japan has already signed an agreement with that country for the recovery, as well as done preliminary surface work

The recovery site is an Australian Government prohibited area and is not accessible to the public. As part of the preparatory work, a field survey of the proposed recovery site in the WPA was conducted with permission from the Australian Government. This preparatory work confirmed the suitability of both the proposed recovery site and the candidate site for the antenna station that will search for the capsule.

The landing of the recovery capsule is now scheduled for late in 2020.

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OSIRIS-REx team picks four finalist sample return sites on Bennu

3:31 pm

After months of photographing and analyzing the very rocky-shrewn surface of the rubble-pile asteroid Bennu, the OSIRIS-REx team has chosen four finalist sites, one of which they will do a touch-and-go sample grab.

This fall, OSIRIS-REx will begin detailed analyses of the four candidate sites during the mission’s reconnaissance phase. During the first stage of this phase, the spacecraft will execute high passes over each of the four sites from a distance of 0.8 miles (1.29 km) to confirm they are safe and contain sampleable material. Closeup imaging also will map the features and landmarks required for the spacecraft’s autonomous navigation to the asteroid’s surface. The team will use the data from these passes to select the final primary and backup sample collection sites in December.

The second and third stages of reconnaissance will begin in early 2020 when the spacecraft will perform passes over the final two sites at lower altitudes and take even higher resolution observations of the surface to identify features, such as groupings of rocks that will be used to navigate to the surface for sample collection. OSIRIS-REx sample collection is scheduled for the latter half of 2020, and the spacecraft will return the asteroid samples to Earth on Sept. 24, 2023.

They given the four sites the names Nightingale, Kingfisher, Osprey and Sandpiper.

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Possibility of meteorites from bright fireball in Ontario

1:54 pm

Astronomers were successfully able to track and photograph a bright fireball over Canada early today, and think it is strongly possible that pieces of it might have hit the ground.

Preliminary results indicate that the fireball first became visible just south of Oshawa over Lake Ontario at an altitude of 93 km. It traveled over Clarington and passed just west of Peterborough before extinguishing just west of Bancroft. The fireball rivaled the full moon in brightness and had a number of bright flares near the end of its flight. The meteoroid was roughly the size of a small beachball (approx. 30cm in diameter) and likely dropped a small number of meteorite fragments in the tens to hundreds of grams size-range on the ground.

Brown and his collaborators at Western and the Royal Ontario Museum are interested in connecting with people from the area of the potential fall, who may have heard anything unusual, or who may have found possible meteorites.

…Meteorites can be recognized by their dark, often scalloped exterior. Usually they will be denser than a ‘normal’ rock and will often be attracted to a magnet due to their metal content. Meteorites are not dangerous, but if recovered, it is best to place them in a clean plastic bag or wrap them in aluminum foil. They should also be handled as little as possible to help preserve their scientific value. In Canada, meteorites belong to the owner of the land upon which they are found. If individuals plan to search, they should always obtain permission of the land-owner before venturing onto private land.

If you live up in that neck of the woods, take a look around. You might find something.

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