A peculiar mix of molecular nitrogen on the comet target of Europe's Rosetta spacecraft may offer clues to the conditions that gave birth to the entire solar system.
Molecular nitrogen was one of the key ingredients of the young solar system. Its detection in Comet 67P/Churyumov–Gerasimenko, which Rosetta is currently orbiting, suggests that the comet formed under low-temperature conditions (a requirement to keeping nitrogen as ice), according to officials with the European Space Agency.
Since nitrogen is also found in planets and moons in the outer solar system, Rosetta's discovery implies that 67P's family of comets formed in the same area, ESA said.
The Rosetta spacecraftdetected the molecular nitrogen using the probe's ROSINA instrument (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) between Oct. 17 and 23, 2014. At the time, Rosetta was orbiting just 6.2 miles (10 kilometers) from Comet 67P's center.
But the finding also carried a surprise: The ratio of molecular nitrogen to carbon monoxide in the comet was 25 times less than what was expected from models of the early solar system. (Carbon monoxide is important for the measurements, because the ice that trapped the molecular nitrogen likely formed at similar temperatures as those needed to trap carbon monoxide.)
Scientists said the unexpectedly low ratio resulted from the way ice is formed at extremely low temperatures. Perhaps the molecular nitrogen was trapped inside "cagelike" water-ice called clathrates, at temperatures between minus 418 Fahrenheit and minus 364 Fahrenheit (minus 250 Celsius and minus 220 Celsius), ESA said.
Alternatively, scientists suggest the ice could have trapped the molecular nitrogen at a temperature of roughly minus 423 F (minus 253 C). This would make sense if 67P had been in the same region of the solar system as Triton and Pluto, which both have nitrogen in their ices.
Regardless of the origin story, 67P would have released the nitrogen as it drew closer to the sun, which caused the comet's ice to melt. This could explain the low ratio, scientists said.
The results were published in the journal Science and led by Martin Rubin, who is with the space research and planetary sciences division of the University of Bern in Switzerland.
ABOARD A JET ABOVE THE NORTH ATLANTIC OCEAN – A total eclipse of the sun on Friday (March 20) thrilled skywatchers across Europe, Africa and Asia where it was visible, but nowhere was the view as perfect as aboard a chartered jet soaring over the top of the world.
Thanks to the German air charter companies AirEvents/Deutsche Polarflug and Eclipse-Reisen, 132 observers from around the world — including this writer — watched the total solar eclipse of 2015 from an airborne jet in what was truly a magnificent sight.
The eclipse watchers, dubbed "umbraphiles" (after the umbra, the dark shadow cone of the moon that rapidly sweeps across the surface of the Earth) flew in two charted aircraft to specifically selected points along the path of totality, situated roughly between the Norwegian Sea and the North Atlantic Ocean, approximately halfway between Norway and Iceland, about 200 miles (320 kilometers) north-northwest of mainland Scotland.
Beyond their scientific and aesthetic interest, total solar eclipses in recent years have become special events with considerable economic impact. Convenient worldwide travel has led to a fraternity of dedicated eclipse chasers who will travel literally anywhere to add a few precious moments of time that they have spent "basking in the shadow of the moon." Indeed, some had paid as much as $8,500 for a window seat on these flights.
Our contingent of eclipse watchers began their adventure from Dusseldorf, Germany. The two aircraft employed were an Airbus A320-200 and a Boeing 737-200, both belonging to the carrier Air Berlin. Dr. Glenn Schneider, from the University of Arizona's Steward Observatory, who was on hand in the latter aircraft for his 32nd total solar eclipse, worked out the flight plans for both flights as well as a third eclipse flight that emanated out of Zurich, Switzerland, to rendezvous with the moon's shadow.
Racing the moon's shadow like paparazzi scrambling alongside a celebrity's passing automobile – a race they would ultimately lose — both aircraft traveling at 520 mph (837 km/h) were still able to lengthen the view of totality by nearly a minute and provide 225 seconds of total eclipse for passengers to take pictures and record other data. In contrast, persons on a hypothetical stationary ship on the open waters below would have seen — provided no clouds blocked the view — the moon's 287-mile-wide shadow (462 km) speed past them at nearly 2,000 mph (3,219 km/h), providing a noticeably shorter total eclipse lasting 167 seconds.
Although for the airborne participants, this morning's amazing sight lasted less than 4 minutes, the fantastically beautiful skyscape more than repaid us all, many of who were already up before dawn to ready themselves for a round-trip flight that would cover nearly 2,000 miles and take almost 5.5 hours.
A gray and gloomy start
The day in Dusseldorf started under cloudy and misty conditions. On the Airbus A320-200, which I was on, we actually got off nearly 6 minutes late, but we quickly broke through the scud, made up the lost time, and soon were on our way for our rendezvous with the lunar shadow. Under the direction of Capt. Wilhelm Heinz and First Officer Dirk Pleimling, and following Schneider's flight plan, we arrived at that special point on an aviator's chart where we were intercepted by the moon's dark shadow precisely on time.
At the moment the last of the sun's rays winked out behind the moon's dark silhouette, it was 18 degrees above the southeast horizon (your clenched fist held at arm's length measures 10 degrees) in a deep blue sky. Below our jet was a nearly solid deck of clouds.
Initially… almost no view!
Interestingly, thanks to the flight trajectory of both aircraft out of Dusseldorf, passengers initially were only able to catch fleeting glimpses of the sun — or no sun at all. The reason was that the sun was situated almost directly behind the planes, mostly precluding us from getting a good view of the promised sky show.
Even though we all knew about an hour after departing Germany that the eclipse was underway, a few joked about whether the long-awaited celestial event was actually happening. "Are they sure this is the right day?" one passenger joked. But in time, as the eclipse slowly progressed and more and more of the sun was being blocked out, many were able to perceive that the skylight outside our windows was slowly getting dimmer.
Totality at last!
The biggest advantage of an eclipse flight is that a view of the totally eclipsed sun is virtually guaranteed. In this case, flying high above the usually tempestuous weather conditions that predominate northernmost Europe and the Arctic, any worries of encountering cloud cover were allayed. Both jets surmounted more than 75 percent of the atmosphere (in terms of mass) and almost all of its water vapor below, providing an opportunity to observe, first-hand, what happens in the Earth's upper atmosphere when the light of the sun is suddenly switched off.
In dramatic fashion just a few minutes before totality, the light inside our cabin began to rapidly fade away, much in the same manner as lights in a theater dim before the start of a show.
As the last of the sun's rays slipped behind the jagged lunar edge, it produced a beautiful and long-lasting "Diamond Ring" effect; to the eye the "diamond" resembled a dazzling magnesium flare, shining with a gleaming silvery white light. The dark lunar shadow then swept in from the west and enveloped the plane in an eerie darkness. Because this moon passed through perigee (its closest point to the Earth) 14 hours before new moon, the shadow that it cast on Earth was unusually large, measuring 287 miles wide by 93 miles long (462 km by 150 km); a tremendous "oval of darkness."
The sun's beautiful corona heralded the beginning of the total phase. Of the 10 total eclipses I've seen, this corona was by far the most brilliant, shining like a globular platinum ring around the moon's black disk; a textbook corona you would see near peak sunspot activity. Adding to this scene was Venus, which shone well off to the east (left) of the sun. Meanwhile, the horizon glowed with the colors of a weird, out-of- place sunset (it was, after all, only 9:41 in the morning).
Variable sky conditions for ground-based observers
Total solar eclipses seem to have a perverse habit of being visible from regions of the Earth where the population is small, as well as remote parts of the Earth or out over wide stretches of open ocean water, and this eclipse was no exception. The total number of people who likely experienced the complete darkening of the sun this morning could have all fit into Dodger Stadium with room to spare. The only places where the moon's umbra touched land were the Faroe Islands (pop. 50,000) and Svalbard (pop. 2,600).
The latter is a Norwegian archipelago in the Arctic Ocean located about midway between continental Norway and the North Pole. In spite of rather poor weather prospects and a warning to watch out for polar bears (which outnumber the local inhabitants), this did not deter more than 1,500 eclipse watchers to journey there in hopes of getting no more than a 2.5-minute glimpse of the darkened sun.
First reports indicated that totality was visible from the Faroes through breaks in rain clouds. Svalbard had variable conditions ranging from crystal-clear skies to clouds, sleet and rain. The path of the total eclipse finally came to an end just short of the North Pole.
The next total solar eclipse will occur in less than year on March 9, 2016, and will sweep over Sumatra, Borneo and Sulawesi (all with poor weather prospects).But on Aug. 21, 2017 — for the first time in nearly four decades — it will be the turn of the contiguous United States to play host to this, the greatest of celestial road shows, with millions of people fortuitously placed within a 70-mile-wide (113 km) totality path that will stretch from Oregon to South Carolina.
THE WOODLANDS, TEXAS—A mysterious bright spot on Ceres, the largest object in the asteroid belt, is looking more and more like ice—and could even be emitting water vapor into space on a daily basis, Dawn mission scientists reported here today at the Lunar and Planetary Science Conference. The bright spot, simply called feature #5, had been noticed before by the Hubble Space Telescope as sitting within an 80-kilometer-wide crater. But the Dawn spacecraft, which went into orbit around Ceres on 6 March, is now close to resolving the feature, which is less than 4 kilometers wide (pictured).
Andreas Nathues, principal investigator for Dawn’s framing camera, says the feature has spectral characteristics that are consistent with ice. Intriguingly, the brightness can be seen even when the spacecraft is looking on edge at the crater rim, suggesting that the feature may be outgassing water vapor above the rim and into space. “Ceres seems to be indeed active,” he says.
The feature brightens through the course of the day, and then shuts down at night. Nathues says the behavior is similar to that of comets. Dawn should be able to resolve the feature completely, along with a smaller companion spot, when the spacecraft dips closer to the dwarf planet in mid-April.
A century ago this year, a young Swiss physicist, who had already revolutionized physics with discoveries about the relationship between space and time, developed a radical new understanding of gravity.
In 1915, Albert Einstein published his general theory of relativity, which described gravity as a fundamental property of space-time. He came up with a set of equations that relate the curvature of space-time to the energy and momentum of the matter and radiation that are present in a particular region.
Today, 100 years later, Einstein’s theory of gravitation remains a pillar of modern understanding, and has withstood all the tests that scientists could throw at it. But until recently, it wasn’t possible to do experiments to probe the theory under extreme conditions to see whether it breaks down.
Now, scientists have the technology to begin looking for evidence that could reveal physics beyond general relativity.
“To me, it is absolutely amazing how well general relativity has done after 100 years,” said Clifford Will, a theoretical physicist at the University of Florida in Gainesville. “What he wrote down is the same thing we use today,” Will told Live Science.
A new view of gravity
General relativity describes gravity not as a force, as the physicist Isaac Newton thought of it, but rather as a curvature of space and time due to the mass of objects, Will said. The reason Earth orbits the sun is not because the sun attracts Earth, but instead because the sun warps space-time, he said. (This is a bit like the way a bowling ball on an outstretched blanket would warp the blanket’s shape.)
Einstein’s theory made some pretty wild predictions, including the possibility of black holes, which would warp space-time to such a degree that nothing inside — not even light — could escape. The theory also provides the foundation for the currently accepted view that the universe is expanding, and also accelerating.
General relativity has been confirmed through numerous observations. Einstein himself famously used the theory to predict the orbital motion of the planet Mercury, which Newton’s laws cannot accurately describe. Einstein’s theory also predicted that an object that was massive enough could bend light itself, an effect known as gravitational lensing, which astronomers have frequently observed. For example, the effect can be used to find exoplanets, based on slight deviations in the light of a distant object being bent by the star the planet is orbiting.
But while there hasn’t been “a shred of evidence” that there’s anything wrong with the theory of general relativity, “it’s important to test the theory in regimes where it hasn’t been tested before,” Will told Live Science.
Testing Einstein’s theory
General relativity works very well for gravity of ordinary strength, the variety experienced by humans on Earth or by planets as they orbit the sun. But it’s never been tested in extremely strong fields, regions that lie at the boundaries of physics.
The best prospect for testing the theory in these realms is to look for ripples in space-time, known as gravitational waves. These can be produced by violent events such as the merging of two massive bodies, such as black holes or extremely dense objects called neutron stars.
These cosmic fireworks would produce only the tiniest blip in space-time. For instance, such an event could alter a seemingly static distance on Earth. If, say, two black holes collided and merged in the Milky Way galaxy, the gravitational waves produced would stretch and compress two objects on Earth that were separated by 3.3 feet (1 meter) by one-thousandth the diameter of an atomic nucleus, Will said.
Yet there are now experiments out there that could potentially detect space-time ripples from these types of events.
“There’s a very good chance we will be detecting [gravitational waves] directly in the next couple of years,” Will said.
The Laser Interferometer Gravitational-Wave Observatory (LIGO), with facilities near Richland, Washington, and Livingston, Louisiana, uses lasers to detect miniscule distortions in two long, L-shaped detectors. As space-time ripples pass through the detectors, the ripples stretch and compress space, which can change the length of the detector in a way that LIGO can measure.
LIGO began operations in 2002 and has not detected any gravitational waves; in 2010, it went offline for upgrades, and its successor, known as Advanced LIGO, is scheduled to boot up again later this year. A host of other experiments also aim to detect gravitational waves.
Another way to test general relativity in extreme regimes would be to look at the properties of gravitational waves. For example, gravitational waves can be polarized, just like light as it passes through a pair of polarized sunglasses.
General relativity makes predictions about this polarization, so “anything that deviates from [these predictions] would be bad” for the theory, Will said.
A unified understanding
If scientists do detect gravitational waves, however, Will expects it will only bolster Einstein’s theory. “My opinion is, we’re going to keep proving general relativity to be right,” he said.
So why bother doing these experiments at all?
One of the most enduring goals of physics is the quest for a theory that unites general relativity, the science of the macroscopic world, and quantum mechanics, the realm of the very small. Yet finding such a theory, known as quantum gravity, may require some modifications to general relativity, Will said.
It’s possible that any experiment capable of detecting the effects of quantum gravity would require so much energy as to be practically impossible, Will said. “But you never know — there may be some strange effect from the quantum world that is tiny but detectable.”