Tag: science

Picking a comet landing site

9:05 am

67P/C-G on August 22, 2014
Comet 67P/C-G as seen on August 22, 2014
from 40 miles. Click on image for full resolution.

Engineers have begun the landing site selection for Rosetta’s Philae lander.

This week, up to ten possible sites are being laid on the table for a first round of dedicated discussions and for the LCC and the SONC to carry out a technical analysis on each site, ready to be presented at the weekend meeting. Participants of the LSSG will then review the results from the technical analysis and discuss the scientific merits of the candidate sites. By the end of the weekend meeting, as many as five sites could be selected for further detailed investigation.

They will announce the five finalist sites on Monday.

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Confirmed: Life in buried Antarctic lake

6:50 pm

American scientists have confirmed that water samples from the buried Antarctic Lake Whillans, first obtained in January 2013, contained almost 4,000 different species of life.

Samples from the lake show that life has survived there without energy from the Sun for the past 120,000 years, and possibly for as long as 1 million years. And they offer the first look at what may be the largest unexplored ecosystem on Earth — making up 9% of the world’s land area. “There’s a thriving ecosystem down there,” says David Pearce, a microbiologist at Northumbria University, UK, who was part of a team that tried, unsuccessfully, to drill into a different subglacial body, Lake Ellsworth, in 2013.

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A problem with drilling on Mars

9:07 am

In drilling a new hole while scientists considered Curiosity’s future route to Mount Sharp, the drill cut off operations prematurely.

Engineers think that the rock might have shifted during drilling, causing the robot rover to abort. They have ordered the rover to take a lot of pictures of the situation so they can figure out what happened.

I should note that engineers take a large risk every time they use Curiosity’s drill, as the design of the rover’s electrical system is such that the drill might short everything out while it operates. Thus, when I see a story about a problem with any drilling operation, I become very concerned. In this case, however, it appears to not be a problem with the rover itself.

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The weight of Comet 67P/C-G

10:26 am

Scientists, using radio and orbital data from Rosetta, have made their first estimate of the mass of Comet 67P/C-G.

For the Rosetta mission, this task comes under the umbrella of the Radio Science Investigation (RSI). Using 80 hours worth of tracking data between 6 August, since arriving at the comet, and up to 9 August, the RSI team made a first estimate of the comet’s mass as approximately 1×10^13 kg +/-10%, or about 10 trillion kilograms.

This is very much a preliminary number which will be refined significantly as the spacecraft continues its travels with the comet.

More here. This mass, when considered in conjunction with the nucleus’s size, suggests a very low density. If you could find an ocean large enough it would float.

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Curiosity retreats from Hidden Valley

3:27 pm

Finding its sandy floor slipperier than expected, engineers have backed Curiosity out of Hidden Valley to drill some holes while they reassess the rover’s route.

The rover’s wheels slipped more in Hidden Valley’s sand than the team had expected based on experience with one of the mission’s test rovers driven on sand dunes in California. The valley is about the length of a football field and does not offer any navigable exits other than at the northeastern and southwestern ends. “We need to gain a better understanding of the interaction between the wheels and Martian sand ripples, and Hidden Valley is not a good location for experimenting,” said Curiosity Project Manager Jim Erickson of JPL. …

Curiosity reversed course and drove out of Hidden Valley northeastward. On the way toward gaining a good viewpoint to assess a possible alternative route north of the valley, it passed over the pale paving stones on the ramp again. Where a rover wheel cracked one of the rocks, it exposed bright interior material, possibly from mineral veins.

More and more, the journey to Mount Sharp appears to be increasingly adventurous for the rover.

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Did Stardust capture stardust?

4:19 pm

Scientists now believe that the spacecraft Stardust captured seven particles from interstellar space during its seven year journey.

Inside the canister, a tennis racket-like sample collector tray captured the particles in silica aerogel as the spacecraft flew within 149 miles (about 240 kilometers) of a comet in January 2004. An opposite side of the tray holds interstellar dust particles captured by the spacecraft during its seven-year, three-billion-mile journey.

Scientists caution that additional tests must be done before they can say definitively that these are pieces of debris from interstellar space. But if they are, the particles could help explain the origin and evolution of interstellar dust. The particles are much more diverse in terms of chemical composition and structure than scientists expected. The smaller particles differ greatly from the larger ones and appear to have varying histories. Many of the larger particles have been described as having a fluffy structure, similar to a snowflake. [emphasis mine]

It appears that for these seven particles, the scientists conclude they are likely interstellar particles because of the speed in which they were traveling when captured as well as their make-up. Both suggest an origin outside the solar system.

However, we should be cautious about this. The data still remains tenuous and preliminary. More work obviously needs to be done to pin this down definitively. More information here.

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Michael Mann’s court suit under attack

10:17 am

Good news: Groups from across the political spectrum are expressing their opposition to Michael Mann’s court suit against his critics.

On Monday, The Reporters Committee for the Freedom of the Press — along with 26 other groups including The Washington Post, Bloomberg and Fox News — filed an “amici curiae,” or “friend of the court,” brief with the D.C. Court of Appeals. An amici curiae is a brief submitted to a court to raise additional points of view to sway a court’s decision.

“While Mann essentially claims that he can silence critics because he is ‘right,’ the judicial system should not be the arbiter of either scientific truth or correct public policy,” the brief states, adding that “a participant in the ‘rough-and-tumble’ of public debate should not be able to use a lawsuit like this to silence his critics, regardless of whether one agrees with Mann or defendants.”

Just as Mark Steyn and Rand Simberg said it, I will say it also: Michael Mann is a fraud. He has no idea what it means to be a scientist, and should have been fired by his university after his climategate emails were uncovered. Instead, his university’s investigation was a whitewash and as much a fraud as Mann is.

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It ain’t gravity holding this asteroid together

1:14 pm

Astronomers have discovered that near Earth asteroid 1950DA is spinning so fast that gravity can’t hold it together. Instead, it is kept whole by cohesive forces called van der Waals forces, predicted but never detected before on an asteroid.

This is the coolest factoid from the article, however:

“We found that 1950 DA is rotating faster than the breakup limit for its density,” said Rozitis. “So if just gravity were holding this rubble pile together, as is generally assumed, it would fly apart. Therefore, interparticle cohesive forces must be holding it together.”

In fact, the rotation is so fast that at its equator, 1950 DA effectively experiences negative gravity. If an astronaut were to attempt to stand on this surface, he or she would fly off into space unless he or she were somehow anchored.

The important take away from this discovery is that it will be very easy to break this kind of asteroid up, turning a large and big threat into a collection of small but harmless rocks.

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Rosetta detects its first dust grains

8:57 am

67P/C-G on August 12, 2014

The Rosetta science team announced today that the spacecraft’s Grain Impact Analyser and Dust Accumulator (GIADA) has captured its first dust grains from Comet 67P/C-G.

Earlier this month, GIADA detected the first four dust grains in its Impact Sensor. The first detection was made on 1 August, when Rosetta was 814 km from 67P/C-G, and about 543 million kilometres from the Sun. Further impacts from three more dust grains were detected on 2, 4, and 5 August, at distances of 603, 286, and 179 km from the comet, respectively.

There is still too little data to come to any firm conclusions about the density and make-up of the coma, but this announcement confirms that the instrument is working as designed. When the comet zips past the Sun at its closest point on August 13, 2015, this instrument will then be able to give us a very good assessment of this particular comet’s behavior as it slowly evaporates.

Meanwhile, the images keep coming. The picture at the top of the post was taken on August 12 from about 64 miles.

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Giant Greek tomb discovered

3:49 pm

Archeologists have uncovered the largest tomb ever discovered in Greece and think it is linked to the reign of Alexander the Great.

The tomb, dating to around 300 BC, may have held the body of one of Alexander’s generals or a member of his family. It was found beneath a huge burial mound near the ancient site of Amphipolis in northern Greece. Antonis Samaras, Greece’s prime minister, visited the dig on Tuesday and described the discovery as “clearly extremely significant”.

A broad, five-yard wide road led up to the tomb, the entrance of which was flanked by two carved sphinxes. It was encircled by a 500 yard long marble outer wall. Experts believe a 16ft tall lion sculpture previously discovered nearby once stood on top of the tomb.

The excavations began in 2012, and by this month hope to identify who actually was buried there.

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The weather is finally changing on Titan

2:14 pm

New Cassini images of Titan have spotted the appearance of clouds above the planet’s northern seas, suggesting the overdue onset of the summer storms that climate models have predicted.

For several years after Cassini’s 2004 arrival in the Saturn system, scientists frequently observed cloud activity near Titan’s south pole, which was experiencing late summer at the time. Clouds continued to be observed as spring came to Titan’s northern hemisphere. But since a huge storm swept across the icy moon’s low latitudes in late 2010, only a few small clouds have been observed anywhere on the icy moon. The lack of cloud activity has surprised researchers, as computer simulations of Titan’s atmospheric circulation predicted that clouds would increase in the north as summer approached, bringing increasingly warm temperatures to the atmosphere there.

“We’re eager to find out if the clouds’ appearance signals the beginning of summer weather patterns, or if it is an isolated occurrence,” said Elizabeth Turtle, a Cassini imaging team associate at the Johns Hopkins University Applied Physics Lab in Laurel, Maryland. “Also, how are the clouds related to the seas? Did Cassini just happen catch them over the seas, or do they form there preferentially?”

Any conclusions drawn at this time about the seasonal weather patterns of Titan must be considered highly uncertain, since we only have been observing the planet for a period that only covers one very short portion of its very long 30 year-long year.

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A blue flask of viruses

9:00 am

The story of the discovery of Ebola.

The next day—September 29—the package arrived: a cheap plastic thermos flask, shiny and blue. I settled down with Guido Van Der Groen—a shy, funny, fellow Belgian aged about thirty, a few years older than I—and René Delgadillo, a Bolivian postdoc student, to open it up on the lab bench. Nowadays it makes me wince just to think of it. Sure, we were wearing latex gloves—our boss insisted on gloves in the lab but we used no other precautions, no suits or masks of any kind.

We didn’t even imagine the risk we were taking. Indeed, shipping those blood samples in a simple thermos, without any kind of precautions, was an incredibly perilous act. Maybe the world was a simpler, more innocent place in those days, or maybe it was just a lot more reckless.

Unscrewing the thermos, we found a soup of half-melted ice: it was clear that subzero temperatures had not been constantly maintained. And the thermos itself had taken a few knocks, too. One of the test tubes was intact, but there were pieces of a broken tube—its lethal content now mixed up with the ice water—as well as a handwritten note, whose ink had partially bled away into the icy wet.

Read it all. The excerpt is from a book length memoir that looks to me to be a very worthwhile read.

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The Milky Way’s most distant stars

11:18 pm

Astronomers have discovered the two most distant stars of the Milky Way.

Both stars are red giants, aging suns that shine so brightly observers can see them from afar. One star is about 890,000 light-years from Earth in the constellation Pisces—33 times farther from the Milky Way’s center than we are and well beyond the edge of the galactic disk. The only other Milky Way member at a comparable distance is a small galaxy named Leo I, which orbits ours at a distance of 850,000 light-years. If the star in Pisces revolves on a circular path as fast as we do, it takes some eight billion years to complete a single orbit around the galaxy. That’s more than half the age of the universe.

The other newfound star is about 780,000 light-years distant in the constellation Gemini and more than a million light-years from the other star. For comparison, the previous record-breaking individual star was only about half a million light-years from Earth.

Both stars are so far outside the galaxy’s disk that it is quite possible that they are not part of the Milky Way at all.

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Another Rosetta closeup of 67P/C-G

4:15 pm

67P on August 8

The above image is not the most recent daily image from Rosetta, but it is the most interesting of the last three.

It shows the side of the comet nucleus that has not been featured in most images, as the topographical differences between its two sections is not as distinctly highlighted. What is highlighted is the neck that connects the two sections, lighter colored and thus likely made up of less dusty ice.

Also of interest here is the circular features on the larger bottom section. These certainly resemble craters, and are likely remnants of early impacts that are now been corroded away as the nucleus’s ice particles evaporate off the surface. The scientific question here is this: Why are crater features more evident on this side and section of the comet nucleus than on other areas of its surface?

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67P from 52 miles

9:32 am

67P from 52 miles, August 7, 2014

The image above was taken on August 7 from only 52 miles. For the first time I had to scale it down slightly so that it would fit on the webpage.

My impression with this image is that there actually might be hints of some very ancient craters at several of the vaguely circular pitted features. For example, look at the large feature on the end of the nucleus’s smaller component on the right. This might be a crater that now is significantly eroded as the comet’s surface evaporated away each time it approached the Sun every 6.5 years.

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Comet 67P on the day of rendezvous

8:39 am

67P/C-G on August 6

The image above was taken at a distance of 60 miles by Rosetta’s navigation camera on August 6, the day the spacecraft rendezvoused and began flying in tandem with it. It looks at the “backside” of the comet, the side where the distinction between its two components is less pronounced. Once again, no obvious craters, and the surface is pockmarked and corroded.

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Rosetta arrives

10:14 am

Rosetta has successfully achieved orbit around Comet 67P/C-G and has transmitted its first close up images. More information here and here about the rendezvous and what science the mission scientists plan to do as they orbit the comet.

The image below is looking down and past the comet’s smaller component as it casts a shadow on the neck and the larger component beyond. As with the earlier images, the comet’s pitted and corroded surface, lacking any obvious craters, is reminiscent to me of a pile of dirty snow that has been dissolving away. In fact, when I lived in New York I would see this kind of look every winter. When the city would get a big snowfall snowplows would push it into large mounds on the side of the road. As time passed these piles would get dirty from the city’s soot and grime, and also slowly melt away. After several weeks it would look almost exactly like the surface of Comet 67P/C-G.

The images and data that will come down from Rosetta over the next year and half as it orbits the comet in its journey around the Sun will be most fascinating. Stay tuned!

67P/C-G up close

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The lingering weak solar maximum

4:36 pm

On Monday NOAA posted its monthly update of the solar cycle, showing the sunspot activity for the Sun in July. As I do every month, I am posting it here, below the fold, with annotations to give it context.

For the first time in four months the decline in sunspots ceased, though the sunspot count hardly rose either. Instead the numbers stayed almost the same in July as they were in June. This was during a month that began with lots of sunspots, and yet saw the first blank sun in almost three years. In fact, the Sun’s activity in July was a roller coaster, as noted by the Solar Influences Data Analysis Center (SIDC) of the Royal Observatory of Belgium.
» Read more

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Eta Carinae’s next big show

9:22 am

Astronomers are gearing up to observe the next binary fly-by of Eta Carinae’s companion star over the next few weeks.

A binary system, η Carinae has two stars that swing past one another every 5.5 years. The bigger star — some 90 times the mass of the Sun — is incredibly unstable, always seemingly on the verge of blowing up. When the smaller companion star makes its closest approach to the primary star, as is happening now, the interaction between the two triggers violent changes in the high-energy radiation pouring out of the system.

Astronomers are watching the show in the hope of learning what drives this enigmatic system. In the 1840s, η Carinae had a mysterious eruption; in recent decades, it has again brightened unexpectedly. “The star is in an awfully deranged state, and no one knows why,” says Kris Davidson, an astronomer at the University of Minnesota in Minneapolis.

Eta Carinae is also famous because it was one of the first objects imaged by Hubble after its repair in 1993, and was thus the first stellar explosion ever caught on camera in a visually sharp and clear manner. (See my book The Universe in a Mirror for that fascinating story.)

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