Tag: science

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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Scientists struggle with earthquake data in the Pacific northwest

10:08 am

The uncertainty of science: A second look at cores drilled in the Pacific northwest has raised doubts about the previous conclusions that the region faces the threat of megaquakes every few centuries.

The bottom line is that though geologists are very confident the northwest faces the threat of future quakes, they can’t yet predict with any confidence their rate or intensity.

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The next U.S. Mars rover will try to make and store oxygen

9:59 am

Of the seven science instruments proposed for the next U.S. Mars rover, scheduled for a 2020 launch date, MOXIE test the engineering to produce and store oxygen, pulled from the Martian atmosphere.

Developed in partnership with NASA’s Jet Propulsion Laboratory, it’s based on the fact that the Martian atmosphere, though extremely thin, is composed of 96 percent carbon dioxide, which means its a vast potential source of oxygen for future explorers and settlers. Essentially, MOXIE is a fuel cell in reverse. Instead of generating electricity by using oxygen to burn a fuel, it uses a process called solid oxide electrolysis , where electricity is employed to split carbon dioxide into oxygen and carbon monoxide.

This process would see Martian air pumped into the unit through a dust filter and pressurized before being passed into a fuel cell. At high temperatures, some ceramic oxides act as oxygen ion conductors. In the fuel cell, a thin, non-porous disc of this ceramic separates two porous electrodes. One electrode acts as the cathode and the other as the anode. Carbon dioxide passes through the cathode and when it comes into contact with the ceramic, the interaction of electricity and the ceramic causes the carbon dioxide to split into oxygen and carbon monoxide. The oxygen and the carbon monoxide are then separated and the oxygen stored.

What makes this unusual is that NASA has actually dedicated one science instrument to engineering research, not pure science. The agency does not do this much anymore, but such research is essential if the U.S. is going to someday send humans to other planets.

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Russian umanned space program pushed back three years

9:32 am

Because of the increased workload imposed on Russia when the U.S. suddenly pulled out of the European ExoMars mission, the Russians have imposed a three year delay on their entire program of unmanned science probes.

Although all previously approved projects still remain on the table, the nation’s series of lunar missions face a domino effect of delays. Russia’s first post-Soviet attempt to land on the surface of the Moon was pushed back from 2016 to 2019. Known as Luna-Glob or Luna-25, the unmanned lunar lander was designed to test landing techniques for future lunar missions. On the political front, the successful landing of the Luna-Glob would be a signal to the international scientific community that Russia is back in the planetary exploration business after the 2011 fiasco of the Phobos-Grunt mission.

This report above is a more nuanced analysis than yesterday’s story about the presentation given by the head of the Russia’s Space Research Institute at Saturday’s science conference in Moscow. Today’s story gives the reasoning for the delays, as explained by the Russians themselves, as well as outlines the entire program more thoroughly.

The story describes a string of planned Russian lunar probes, beginning with Luna-Glob. This program was probably approved by the government when the U.S. decided to return to the Moon in 2004 under George Bush. The Russians don’t seem to be able any longer to be self-starters, but instead need the competition from the U.S. to get them jump-started.

Even so, while the U.S. has already flown most of the unmanned probes to the Moon that were proposed in 2004, the Russian program had not yet gotten off the ground.

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67P from less than 200 miles

9:15 am

67P on August 3

Today’s Rosetta image of Comet 67P, shown above, gives us a different angle of the comet. The spacecraft was only 186 miles (300 kilometers) away when it snapped the picture, and this side view emphasizes the nucleus’s jagged shape.

I am reminded of what happens to a block of ice when you spray warm water on it. It begins to melt away, but very randomly and unevenly, producing very weird shapes and the surface evaporates off. In the case of Comet 67P, the nucleus is a dirty ball of ice, and the Sun’s rays have been causing its surface to evaporate off every time it approaches the Sun. Thus, we get a very weird shape.

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Today’s Comet 67P image

9:05 am

Comet 67P on August 2

The image above was taken on August 2 using Rosetta’s navigation camera. It has been processed by the science team to bring out the details. I have also rotated it to match the August 1 image taken at a distance of 620 miles that was taken by Rosetta’s OSIRIS narrow angle camera, designed to do the actual science.

You can see that the navigation camera does a pretty good job on its own of capturing the comet’s nucleus. Both images show that the instruments are working perfectly, and thus tell us that the next few months will be quite spectacular after Rosetta goes into orbit in three days, followed in November by the landing of Philae somewhere on the comet’s surface.

If you download both images and then switch back and forth between them you can get a better feel for the geometry of the surface features.

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Ebola patient arrives in U.S.

12:11 am

Doctors in charge of the specialized isolation unit for treating dangerous infectious diseases are confident that they will be able to treat the infected patients safely without the disease escaping.

I have complete confidence that a well run facility like this, with modern technology, could keep the disease isolated. The key words, however, are “well run.” I pray that this description still applies to Emory University Hospital.

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Comet 67P from 1000 k

11:06 pm

67P from 1000 kilometers

Above is a new image of Comet 67P as seen from about 1000 kilometers, or about 620 miles, released by the Rosetta science team today. The image was taken on August 1 and has been processed somewhat to bring out the details. The black spot near the junction between the nucleus’s two sections is not real but an artifact of the camera’s CCD.

This image is the first real clear and sharp look at the nucleus, and what it shows us is a surface quite different from the many other asteroids that science probes have imaged close-up in the past. From this angle there are far few craters visible then is normally seen on asteroids, and the surface has complex roughness and pitted look that I suspect the planetary geologists are right now scratching their heads about and waving their arms trying to explain. My first guess, which no one should take too seriously, is that as material vents off the comet when it gets close to the Sun it leaves behind these scars.

One more thing: If you go here you can see a number of additional image releases in the last 24 hours, all fascinating. This link explains that the features that looked like craters in earlier images were actually artifacts from the camera’s CCD.

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Don’t buy stock yet in that “impossible” space drive

7:46 pm

The uncertainty of science and engineering: A physicist takes a close and skeptical look at the “impossible” space drive that NASA engineers discovered seemed to work. Key quote:

“All in all,” Lee concluded, “it will take a lot more information before we can judge whether the thrust is really a thrust or not.”

Read the whole article. They point out the areas of doubt and weakness, as well as the possibilities.

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Getting closer

8:29 am

Comet 67P on July 31

This image of Comet 67P from Rosetta was taken yesterday. Though it has not been processed like the image I posted yesterday, more details continue to come out as the spacecraft each day gets closer to the comet. This image was taken from a distance of 825 miles, 375 miles closer than the previous day.

Very soon these close-up images will become too large to show the entire nucleus in one image. Rosetta will instead begin to snap images of specific features.

Meanwhile, the Rosetta science team released its first temperature readings of the comet.
» Read more

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Fermi proves that novae produce gamma rays

12:56 pm

The Fermi Gamma-Ray Space Telescope has discovered that novae, small scale stellar explosions similar to some supernovae but far less powerful, also produce gamma rays when they explode.

A nova is a sudden, short-lived brightening of an otherwise inconspicuous star caused by a thermonuclear explosion on the surface of a white dwarf, a compact star not much larger than Earth. Each nova explosion releases up to 100,000 times the annual energy output of our sun. Prior to Fermi, no one suspected these outbursts were capable of producing high-energy gamma rays, emission with energy levels millions of times greater than visible light and usually associated with far more powerful cosmic blasts.

What is significant about this is that it demonstrates a solid link between novae and supernovae, since only recently have scientists shown that some supernovae also produce gamma ray bursts. It suggests that the two explosions are produced by somewhat similar processes, but at very different scales. This fact will have important ramifications in the study of stellar evolution and the death of stars. For example, some nova stars often go nova repeatedly. Other data suggest that some more powerful eruptions can be recurrent as well. Extending this recurrent pattern to supernova suggests many new theoretical possibilities.

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How the Earth gave the Moon a lemon shape

9:36 am

Scientists have found that the Earth’s gravity combined with the Moon’s rotation forced the satellite to become “lemon-shaped.”

As the Moon solidified, its rotation caused it to elongate along its polar axis. But because the length of the Moon’s rotation was the same as its orbit, with one hemisphere always facing the Earth, the tidal force of the Earth’s gravity then pulled at the center, distorting the Moon’s shape so that one hemisphere bulged Earthward.

This theory is not new, but these new calculations are more robust, lending greater weight to it.

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The early bombardment of the Earth

9:04 am

Using computer models based on the Moon’s crater record, scientists have developed a simulation of the great early bombardment of the Earth around 4 billion years ago.

The model suggests that the biggest asteroids to hit Earth would have been as large as 3,000 kilometres across. Between one and four would have been 1,000 kilometres wide or larger, it predicts, with a total of three to seven exceeding 500 kilometres in width. The most recent of these would have hit around 4.2–4.3 billion years ago.

In comparison with Earth’s mass, the amount of rock hitting the planet would have been tiny. But it would have had an enormous effect on Earth’s surface, says Marchi. A 10-kilometre-wide asteroid was enough to kill the dinosaurs, and studies4 show that one 500 kilometres across would vaporize all of the planet’s oceans. “At 1,000 kilometres, the effects would be so wide the planet would probably be completely resurfaced with material from the mantle,” he says.

More here, including animated gifs showing this bombardment unfold.

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