Tag: asteroids

New Horizons’ future research goals

9:15 am

On Monday at a planetary science conference Alan Stern, the project scientist for New Horizons, outlined the science goals in studying the Kuiper Belt should the spacecraft’s mission be extened through 2021.

The main goal will be the January 1, 2019 fly-by of Kuiper Belt object 2014 MU69, estimated to be between 12 to 24 miles across. However, the proposal also includes the following:

“In addition to making a close flyby of MU69, we’re also going to be close enough in range to study quite a number of other small KBOs, and some large ones that are on the Pluto scale,” Stern said. New Horizons will be able to study them in ways that could never be accomplished from Earth. The closeness of the spacecraft will enable high resolution observations, and the ability to look for satellites that cannot be seen from Earth observatories or with the Hubble Telescope.

“Because we are looking back on the rest of the solar system, at the Kuiper Belt and the Centaur Population,” Stern said, “we’re going to be able to study another 18 or 20 small bodies to determine whether or not the recently discovered rings around the centaur Chariklo are a common occurrence, or something anomalous. And I don’t know of any other way over the next several years, except through New Horizons, that we can develop a data set like that.”

What I find amazing is that it appears from Stern’s remarks that NASA has not yet approved this proposal. Before the team discovered 2014 MU69, I would have been more skeptical about extending the mission, but since they will be able to do a close fly-by of a type of object never before seen, and considering the time and cost it takes to get to the Kuiper Belt, it seems foolish now to not approve this mission extension.

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New close-up of Occator Crater’s spots

1:57 pm

Occator Crater central spot

The Dawn science team have released new images taken from the spacecraft’s low orbit observations, including a close-up of the central white spot at Occator Crater, the brightest spot on Ceres.

The image on the right is a cropped though full resolution version of the full image. I have reduced it only slightly. As they note,

Occator Crater, measuring 57 miles (92 kilometers) across and 2.5 miles (4 kilometers) deep, contains the brightest area on Ceres, the dwarf planet that Dawn has explored since early 2015. The latest images, taken from 240 miles (385 kilometers) above the surface of Ceres, reveal a dome in a smooth-walled pit in the bright center of the crater. Numerous linear features and fractures crisscross the top and flanks of this dome. Prominent fractures also surround the dome and run through smaller, bright regions found within the crater.

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Changes in Ceres’s white spots

3:56 pm

The uncertainty of science: Ground-based observations of Ceres now suggest that the white spots imaged by Dawn undergo subtle unexpected variations

As Ceres rotates every 9 hours, HARPS is so sensitive that it can detect the very slight Doppler shift in spectrum frequency as the bright spots rotate toward and away Earth, but during observations for 2 nights in July and August 2015, more changes not related to Ceres’ spin were detected. “The result was a surprise,” said co-author Antonino Lanza, also from the INAF–Catania Astrophysical Observatory. “We did find the expected changes to the spectrum from the rotation of Ceres, but with considerable other variations from night to night.”

And it appears that these changes are consistent with some kind of volatile (ice) being exposed to sunlight and venting vapor into space, causing an increase in reflectivity. It seems that when Occator experiences solar heating, plumes are produced and then evaporate, creating a complex spectroscopic signal that evolves during that hemisphere’s daytime. This finding appears to be consistent with earlier observations made by Dawn showing a mysterious haze over Occator.

The problem with this theory is that it assumes the white spots are comprised of water ice. However, data from Dawn has instead suggested that the white spots are not water but salt deposits.

It could be that the white spots are salt left behind when water vented from inside Ceres evaporates away, but so far the data from Dawn has not found any evidence of water at the spots. If it was venting there, Dawn should have seen it.

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Ceres’s big mountain

10:26 pm

Ahuna Mons on Ceres

The Dawn science team has released an oblique angle image of Ceres’s big mountain, Ahuna Mons. I have cropped and reduced it above to show it here.

Despite looking almost toylike in this image, the mountain is quite monstrous, especially considering Ceres’s relatively small size.

This mountain is about 3 miles (5 kilometers) high on its steepest side. Its average overall height is 2.5 miles (4 kilometers). These figures are slightly lower than what scientists estimated from Dawn’s higher orbits because researchers now have a better sense of Ceres’ topography.

Consider: Mount Everest is not quite six miles high, on a planet with a diameter about 7926 miles across. Ceres however is only about 600 miles across at its widest, which means a 3 mile high mountain is 0.5% of Ceres’s entire width! Such a thing could only occur on such a small body, whose gravity is not quite great enough to force things into a completely spherical shape. It is for this reason it could be argued that Ceres doesn’t qualify as a dwarf planet, but would be better labeled a giant asteroid.

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Dawn’s chief engineer reviews the mission

8:45 am

In a long and very detailed post, the chief engineer and mission director of Dawn gives us a very detailed update on the successful state of the spacecraft’s mission.

Not only does he describe what has been gathered at Ceres since the spacecraft arrived a year ago, he gives us this crucial information about the state of this paradigm-shattering ion engine spacecraft, the first to travel to two different objects in the solar system:

Dawn has faced many challenges in its unique voyage in the forbidding depths of space, but it has surmounted all of them. It has even overcome the dire threat posed by the loss of two reaction wheels (the second failure occurring in orbit around Vesta 3.5 years and 1.3 billion miles, or 2.0 billion kilometers, ago). With only two operable reaction wheels (and those no longer trustworthy), the ship’s remaining lifetime is very limited.

A year ago, the team couldn’t count on Dawn even having enough hydrazine to last beyond next month. But the creative methods of conserving that precious resource have proved to be quite efficacious, and the reliable explorer still has enough hydrazine to continue to return bonus data for a while longer. Now it seems highly likely that the spacecraft will keep functioning through the scheduled end of its primary mission on June 30, 2016.

NASA may choose to continue the mission even after that. Such decisions are difficult, as there is literally an entire universe full of interesting subjects to study, but resources are more limited. In any case, even if NASA extended the mission, and even if the two wheels operated without faltering, and even if the intensive campaign of investigating Ceres executed flawlessly, losing not an ounce (or even a gram) of hydrazine to the kinds of glitches that can occur in such a complex undertaking, the hydrazine would be exhausted early in 2017. Clearly an earlier termination remains quite possible.

Dawn has proven the value of ion engines. I would expect to see them used many more times in the future, especially missions heading to low gravity environments.

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The cratered surface of Ceres

5:23 pm

Craters on Ceres

Cool image time! As Dawn continues its survey of Ceres the science team is beginning to release images looking sideways at the planet, rather than straight down, in order to get a better understanding of the topography. The image to the right is an example. It shows the area around 37-mile-wide Fluusa Crater. I have cropped it to emphasize the most rugged areas, especially the jagged cliff meandering away towards the horizon.

This image provides a hint at the differences between Ceres and the Moon. Up until now Dawn images have given the impression that Ceres is very much like the heavily cratered lunar surface. The terrain in this image however suggests to me that Ceres’ surface crust is much less dense because of the low gravity, and thus has a light puffy feel to it. The Moon’s surface is rarely this uneven, as its higher gravity has pounded things down, smoothing them out somewhat.

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Tests confirm meteorite at India impact site

9:53 am

The uncertainty of science: Even as NASA officials poo-poo the suspected meteorite impact in India that killed a bus driver, India scientists have done a chemical analysis of one of the rocks found near the site and found it to be a meteorite fragment.

According to a preliminary report by National College Instrumentation Facility (NCIF) in Trichy, a Scanning Electron Microscope (SEM) study on samples retrieved from the campus in Vellore where the blast occurred shows the “presence of carbonaceous chondrites”.

“Carbonaceous denotes objects containing carbon or its compounds and chondrites refer to non-metallic meteorite parts containing mineral granules,” K Anbarasu, a geologist who is also principal of the Trichy-based National College, told The Indian Express.

There remains uncertainty because the fragments tested did not actually come from the impact crater itself.

Anbarasu said the preliminary SEM study was conducted on “small pieces of black material” found near the blast site. “The crater formed at the spot had been already disturbed by other investigators. So we inspected the entire campus as any meteor incident would scatter several objects across the area before landing. Finally, we spotted several small pieces of this black material, one the size of a paperweight, on the terrace of a building nearby,” Anbarasu said.

Nonetheless, I think it unprofessional and inappropriate for a NASA official to comment on this event half a globe away. There is no way that they can really determine anything from the available photos taken of the impact site, and thus they should shut up.

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The first recorded human death from a meteorite?

8:41 am

Officials in India are reporting what could be the first recorded death of a human by meteorite impact.

According to local reports, a bus driver was killed on Saturday when a meteorite landed in the area where he was walking, damaging the window panes of nearby buses and buildings. Three other people were injured.

The story is not yet confirmed, and could easily be proven wrong.

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Flying over Ceres

8:43 am

The Dawn science team has released a new animation using the images taken by the spacecraft. The colors have been enhanced to emphasize the geological differences on the surface. I have embedded it below the fold.

The movie was produced by members of Dawn’s framing camera team at the German Aerospace Center, DLR, using images from Dawn’s high-altitude mapping orbit. During that phase of the mission, which lasted from August to October 2015, the spacecraft circled Ceres at an altitude of about 900 miles (1,450 kilometers).

» Read more

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Comet 67P/C-G’s active surface

9:28 am

Comet 67P/C-G's active surface

Cool image time! The Rosetta science team today released a spectacular image, taken by Rosetta’s high resolution camera, of the surface of Comet 67P/C-G. A cropped version is above and below the fold. A cropped version of the full image, focusing in on the smooth and active area dubbed Imhotep, is above.

This smooth dusty terrain, which covers about 0.8 sq km, is etched with curvilinear features stretching hundreds of metres and which have been found to change in appearance over time. Many large boulders are also seen scattered within the smooth terrain, including the boulder Cheops in the foreground. Smaller but more numerous boulders are associated with exposed cliff faces and are most likely the product of erosion. In some debris falls, detailed analysis has revealed the presence of water ice.

I have also included, below the fold, a second close-up crop from this same image, showing the layered cliffs to the left of Imhotep as well as several mysterious as-yet not understood round features at the cliff’s base.
» Read more

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Dantu Crater on Ceres

11:30 am

bright areas on crater wall on Ceres

Cool image time! As Dawn continues its close survey of Ceres, the science team has released this image of Dantu Crater, showing the bright spots on its rim as well as fractures on the crater floor. The picture was taken in December and has a resolution of about 120 feet per pixel.

Though scientists now favor salt deposits of some kind as the cause of the bright areas on Ceres, they also recognize that this theory is not yet proven. Moreover, the theory suggests that the salt was deposited as part of a water brine. When the water in the brine evaporated away, it left the salt behind. The problem, however, is that we do not yet have direct evidence that there is any water on Ceres at all, either on the surface or in the interior, which makes this theory exceedingly uncertain.

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Astronomers propose Neptune-sized planet in Kuiper Belt

9:13 am

The uncertainty of science: Using the orbital data of many recently discovered Kuiper Belt objects [KBOs], two astronomers have proposed the existence of a planet ten times the mass of the Earth and orbiting the sun every 20,000 years.

Trujillo and Sheppard had noted that Sedna, VP113, and several other KBOs all shared a peculiar property: their closest approach to the Sun lay in the plane of the Solar System, and they all moved from south to north when crossing that plane. Batygin and Brown analyzed the orbits further and discovered that their long axes were physically aligned, too, as if something had nudged them to occupy the same region of space around the Sun. The team concluded that a massive object must be shepherding the objects. “We have a gravitational signature of a giant planet in the outer Solar System,” Batygin says.

Planet Nine — informally known as Phattie — is probably smaller than Neptune and icy with a gassy outer layer. The gravitational effect of Uranus and Neptune would have flung it outward in the first 3 million years of the Solar System’s existence, Batygin says.

Be warned! The existence of this as-yet unseen giant planet is quite uncertain. The orbits of the KBOs they are using to postulate its existence have only been observed for a very short period and have not been completely mapped. Thus, those orbits themselves are very uncertain. Moreover, we so far have a very incomplete census of the Kuiper Belt. The orbital behavior used as evidence of another planet could also be caused by many other known factors that have not yet been observed.

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