Tag: science

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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ExoMars will likely miss 2018 launch date

9:06 am

Because of technical and financial issues the European/Russian ExoMars rover mission is expected to miss its 2018 launch window.

The main reason for the delay would be the ExoMars’ brand-new landing system, which is designed to safely take the rover through a fiery descent in the Martian atmosphere and then softly land it on the surface of the Red Planet.

In addition to its late development start, the landing system has a complicated share of responsibilities between Russia and Europe, which greatly slows down the work. For example, the overall landing system is being developed by NPO Lavochkin in Moscow, while its parachute system will be provided by Europe. Many other aspects of the mission are similarly intertwined.

To further complicate matters, NPO Lavochkin, which traditionally builds all Russian planetary probes, but also some of the highly classified military satellites, is notorious for its Soviet-style secrecy. As a result, it is harder for the two sides to coordinate the work, Europeans sources said. Finally, the translation of documents between Russian and English further delays the work on the project.

The program is also significantly over budget.

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The Milky Way shrinks

9:49 pm

The uncertainty of science: New research by astronomers suggests that the Milky Way is about half as massive as previously estimated.

In the sixties I remember astronomers claiming that the Milky Way was twice as big as Andromeda. Then it was considered half as big. Most recently it was considered about the same size. This new research makes it half as big as Andromeda again.

In other words, the data is very uncertain, and the scientists really don’t have a good handle on it. None of these conclusions should be taken very seriously. All we really know at this point is that the Milky Way and Andromeda are approximately comparable.

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ISEE-3 engine restart fails but the private effort continues

11:57 am

After numerous tries, the private effort to put ISEE-3 back into its original orbit has failed.

We have completely accomplished all of our original goals except for one: firing the ISEE-3 propulsion system in a sufficient fashion to alter its trajectory. We did operate the propulsion system briefly so as to correct the spin of the spacecraft, and to start the trajectory correction maneuver. The propulsion system works fine. The problem is that there is no longer any Nitrogen pressurant left in its tanks to allow it to work.

36 years and more than 30 billion miles have taken its toll on the spacecraft’s propulsion system. We have exhausted every option to bring the engines online so as to conduct the correction maneuver required to place it in its planned orbit. Without the pressurant it just won’t work.

Have they given up? No! Though the spacecraft will remain in a solar orbit where maintaining communications will be difficult if not impossible, they are going to try anyway, and are even going to run another crowd-sourcing campaign to finance it.

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Gaia commissioning complete

9:47 am

After several months of in-orbit analysis, engineers have declared the European space telescope Gaia ready to begin research.

There have been several issues that had raised concerns, but from the article it sounds as if the engineers have either corrected the problems or have found ways to overcome or mitigate them.

Gaia will measure the movement and location of a billion stars, allowing astronomers to map the Milky Way better than ever before.

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Venus Express is alive

9:03 am

After diving into Venus’s atmosphere on an aerobraking test that could have destroyed the spacecraft, the European probe Venus Express has now successfully used its last bits of fuel to raise its orbit back to research height.

Its present orbit will probably decay sometime in December, when the spacecraft will burn up in the atmosphere. However, the scientists running the mission though that was likely to happen during the aerobraking maneuver. Instead, Venus Express is giving them about another half year of research.

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