UPDATE: Comet Flyby Mars’ Magnetic Field and Charged Particles

Jared Espley, a MAVEN science team member at NASA’s Goddard Space Flight Center said; “Comet Siding Spring plunged the magnetic field around Mars into chaos. We think the encounter blew away part of Mars’ upper atmosphere, much like a strong solar storm would.”

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Mars’ atmosphere was very much like Earth’s – that is until an interplanetary collision occurred ripping its protective magnetic field away. However, some managed to remain after the event, additionally; current seasonal climate change continues to produce upper atmospheric plasma which is in fact charged particles.

Comet Siding Spring is also surrounded by a magnetic field as a result of solar wind interacting with plasma generated in the coma, which is the large mass we see as a gaseous cloud. Comet Siding Spring’s nucleus, as are all comets, just a tiny asteroid with remaining ice. In this case, its nucleus is approximately .3 miles (.5 km) in diameter. However, the coma, as with all comets, stretches some 600,000 miles (1,000,000 km) in distance.

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As a result of Earth’s magnetic field weakening with increasing amounts each year, it is time to reconsider the effects of NEOs (Near Earth Orbits). Comets create their own atmosphere by outgassing which contributes to its generating of charged particles. What is less known, is that although asteroids do not have an atmosphere, they do retain predominantly positively charged cosmic rays. They would mostly burnout during entry through Earth’s atmosphere, but as we know, the large ones make it through.

But it is time to recalibrate. Due to a weakening magnetic field, it might be wise to view the small guys with a little more interest and be a little less ambivalent when we hear the newscaster say in their jocular playful manner: “hey, did you hear about the near miss we had last night….

Red Sprites At The Edge Of Space

Solar activity is very low. Nevertheless, space weather continues. High above late-summer thunderstorms in Africa, red sprites are dancing across the cloudtops, reaching up to the edge of space itself. Astronauts onboard the International Space Station photographed this specimen (circled) on March 14th.

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Sprites are an exotic form of “upward lightning.” They are a true space weather phenomenon, inhabiting the upper reaches of Earth’s atmosphere alongside meteors, and some auroras. Some researchers believe sprites are linked to cosmic rays: subatomic particles from deep space striking the top of Earth’s atmosphere produce secondary electrons that, in turn, could provide the spark that triggers the elaborate red forms.

Although sprites have been seen for at least a century, most scientists did not believe they existed until after 1989 when sprites were photographed by cameras onboard the space shuttle. They have since been photographed many times from the ISS.

NASA Station Leads Way for Improved Measurements of Earth Orientation, Shape

NASA has demonstrated the success of advanced technology for making precise measurements of Earth’s orientation and rotation – information that helps provide a foundation for navigation of all space missions and for geophysical studies of our planet.

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The technology includes a new class of radio antenna and electronics that provide broadband capabilities for Very Long Baseline Interferometry, or VLBI. This technique is used to make precise measurements of Earth in space and time.

VLBI measurements have been conducted for decades using a worldwide network of stations that carry out coordinated observations of very distant astronomical objects called quasars. To meet the demand for more precise measurements, a new global network of stations, called the VLBI Global Observing System, or VGOS, is being rolled out to replace the legacy network.

NASA is participating in this next-generation network and just completed the installation of a joint NASA-U.S. Naval Observatory VGOS station at NASA’s Kōke‘e Park Geophysical Observatory in Hawaii. NASA has two other developmental VGOS stations operating at the Goddard Geophysical and Astronomical Observatory at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and at the Massachusetts Institute of Technology’s Haystack Observatory in Westford, Massachusetts.

With this preliminary network, NASA passed a crucial milestone on February 5: conducting the first demonstration anywhere in the world of broadband observations for VLBI over a long baseline.

“The successful tests demonstrate the viability of the new broadband antenna technology for making the kinds of observations needed for improved accuracy in measurements of the very fine-scale shape of Earth,” said Benjamin R. Phillips, who leads NASA’s Earth Surface and Interior Focus Area at NASA Headquarters in Washington, D.C.

The coordinated observation was verified by detection of fringes – an interference pattern indicating that all three stations were receiving and could combine the signals from the quasar they observed.

“The testing has been a concerted effort involving many team members at all three stations, as well as the MIT correlator facility,” said Pedro Elosegui of the Haystack Observatory, which leads the NASA development of the VGOS signal chain.

Several technical hurdles had to be cleared to carry out the long-baseline demonstration. One issue is that the effects of the ionosphere – a layer of Earth’s upper atmosphere that impacts the behavior of radio waves – and of the local weather are quite different at the three sites. Another factor, which applies in any VLBI measurement, is that stations have to contend with interference from nearby radio and cell towers and other sources.

“These and other technical issues have been dealt with,” said Goddard’s Stephen Merkowitz, manager of NASA’s Space Geodesy Project. “We have a few more challenges down the road, but they are manageable. We now know that the new global system can be used the way it was intended.”

The broadband antenna and electronics provide improved sensitivity in a scaled-down package. With dish sizes of 12 to 13 meters (about 39 to 42 feet), the next-generation antennas are designed to be smaller than most of the current system’s dishes, which are typically 20 to 30 meters (about 65 to 100 feet). The scaled-down size allows an antenna to move quickly, conducting up to 100 observations in an hour compared to about 12 observations in an hour for the current VLBI system. This type of antenna is also much less expensive than the larger antennas, making it more economical to deploy and operate a global network.

Broadband capability makes it possible to conduct observations in four bands – that is, at four frequencies – at the same time, whereas current VLBI systems operate in two bands. With four bands, more bits can be recorded at once, so the broadband system can achieve data rates of 8 to 16 gigabits per second, which is about 1000 times the data rate for HDTV. (The current VLBI system has a typical rate of 256 megabits per second.) This leads to better sensitivity, even though the antenna is smaller.

Another new feature is that the four bands are selectable within a range of 2 gigahertz to roughly 14 gigahertz. This helps to avoid interference with other sources, such as radio and cellphone towers.

With the rollout of the VGOS network, existing VLBI stations are being replaced, or in some cases upgraded. More sites will be added in the future to provide more uniform coverage across the globe. Once fully implemented, the worldwide VGOS network is expected to yield position and Earth orientation measurements that improve precision by a factor of three or more, compared to current measurements.

“The next-generation VLBI system will expand our ability to make the kinds of measurements that will be needed for geophysical studies and navigation applications, which demand more precision all the time,” said Merkowitz.

Warming Ocean Water Undercuts Antarctic Ice Shelves

“Upside-down rivers” of warm ocean water threaten the stability of floating ice shelves in Antarctica, according to a new study led by researchers at the University of Colorado Boulder’s National Snow and Ice Data Center published today in Nature Geoscience. The study highlights how parts of Antarctica’s ice sheet may be weakening due to contact with warm ocean water.

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“We found that warm ocean water is carving these ‘upside-down rivers,’ or basal channels, into the undersides of ice shelves all around the Antarctic continent. In at least some cases these channels weaken the ice shelves, making them more vulnerable to disintegration,” said Karen Alley, a Ph.D. student in CU-Boulder’s Department of Geological Sciences and lead author of an analysis published today in Nature Geoscience.

Ice shelves are thick floating plates of ice that have flowed off the Antarctic continent and spread out onto the ocean. As ice shelves flow out to sea, they push against islands, peninsulas, and bedrock bumps known as “pinning points.” Contact with these features slows the flow of grounded ice off the continent. While ice shelves take thousands of years to grow, previous work has shown that they can disintegrate in a matter of weeks. If more ice shelves disintegrate in the future, loss of contact with pinning points will allow ice to flow more rapidly into the ocean, increasing the rate of sea level rise.

“Ice shelves are really vulnerable parts of the ice sheet, because climate change hits them from above and below,” said NSIDC scientist and study co-author Ted Scambos. “They are really important in braking the ice flow to the ocean.”
The features form as buoyant plumes of warm and fresh water rise and flow along the underside of an ice shelf, carving channels much like upside-down rivers. The channels can be tens of miles long, and up to 800 feet “deep.”

When a channel is carved into the base of an ice shelf, the top of the ice shelf sags, leaving a visible depression, or “wrinkle”, in the relatively smooth ice surface. Alley and her colleagues mapped the locations of these wrinkles all around the Antarctic continent using satellite imagery, as well as radar data that images the channels through the ice, mapping the shape of the ice-ocean boundary.

The team also used satellite laser altimetry, which measures the height of an ice shelf surface with high accuracy, to document how quickly some of the channels were growing. The data show that growing channels on the rapidly melting Getz Ice Shelf in West Antarctica can bore into the ice shelf base at rates of approximately 10 meters (33 feet) each year.

The mapping shows that basal channels have a tendency to form along the edges of islands and peninsulas, which are already weak areas on ice shelves. The team observed two locations where ice shelves are fracturing along basal channels, clear evidence that basal channel presence can weaken ice shelves to the point of breaking in vulnerable areas.

Ice shelves are thick floating plates of ice that have flowed off the continent and out onto the ocean. As ice shelves flow out to sea, they push against islands, peninsulas, and bedrock bumps known as “pinning points”. Contact with these features slows the ice flowing off the continent. If ice shelves disintegrate in the future, loss of contact with pinning points will allow ice to flow more rapidly into the ocean, increasing rates of sea level rise.

While no ice shelves have completely disintegrated due to carving by basal channels, the study points to the need for more observation and study of the features, said co-author… “It’s feasible that increasing ocean temperatures around Antarctica could continue to erode ice shelves from below.”

Model Suggests 1812 San Andreas Earthquake May Have Been Set Off By San Jacinto Quake

An assistant researcher professor with California State University has found evidence that the powerful quake that struck southern Californian back in 1812 may have been precipitated by a fault line other than the San Andreas. In his paper published in the journal Science Advances, Julian C. Lozos describes a computer model he created using real world data, what it showed, and why his findings suggest that a future double earthquake could occur someday in the area.

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Back in 1812 a major earthquake struck southern California near what is now San Bernardino—modern study of damage from the quake suggested it was approximately a magnitude 7.5 quake. There was little damage because there were few structures in the area back then, though approximately 40 people were killed when a church they were in collapsed. For many years, Earth scientists have assumed that the quake was due solely to activity along the San Andreas Fault. In this new effort, Lozos suggests that the quake may have actually been set off by a quake along the San Jacinto fault line.

Lozos’ findings are part of a study that included field trips to several sites in an area where the San Andreas Fault and the San Jacinto Fault nearly merge. While there, he found evidence of three strands—where sections of fault are separated by bits of crust that has remained intact—one near the San Andreas fault and two near the San Jacinto fault. Each strand is evidence of an earthquake, but reports from people in the area suggest there were only two earthquakes during the time period under study—in 1812 and 1800, which suggested that one of the strands on the San Andreas Fault and one on the San Jacinto Fault were evidence of the same quake. Lozos also looked at other data collected by other researchers doing working on faults in the area—all of it went into a model he built to describe seismic activity in the area surrounding the time frame of the 1812 quake. The model showed that the most likely scenario that could account for the data that has been collected was that a quake had occurred along the San Jacinto fault line and as it made its way near the San Andreas fault line, the disruption caused a quake to occur along that fault line as well.

Lozos is quick to point out that his model is just that and that thus far he has no evidence to suggest that such a double quake is imminent, but he also notes that if it happened before, it could happen again, noting that southern California is long overdue for a pretty big tumbler.

Clocking The Rotation Rate Of A Supermassive Black Hole

A recent observational campaign involving more than two dozen optical telescopes and NASA’s space based SWIFT X-ray telescope allowed a team of astronomers to measure very accurately the rotational rate of one of the most massive black holes in the universe. The rotational rate of this massive black hole is one third of the maximum spin rate allowed in General Relativity. This 18 billion solar mass heavy black hole powers a quasar called OJ287 which lies about 3.5 billion light years away from Earth. Quasi-stellar radio sources or `quasars’ for short, are the very bright centers of distant galaxies which emit huge amounts of electro-magnetic radiation due to the infall of matter into their massive black holes.

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This quasar lies very close to the apparent path of the Sun’s motion on the celestial sphere as seen from Earth, where most searches for asteroids and comets are conducted. Therefore, its optical photometric measurements already cover more than 100 years. A careful analysis of these observations show that OJ 287 has produced quasi-periodic optical outbursts at intervals of approximately 12 years dating back to around 1891. Additionally, a close inspection of newer data sets reveals the presence of double-peaks in these outbursts.

These deductions prompted Prof. Mauri Valtonen of University of Turku, Finland and his collaborators to develop a model that requires the quasar OJ287 to harbour two unequal mass black holes. Their model involves a massive black hole with an accretion disk (a disk of interstellar material formed by matter falling into objects like black holes) while the comparatively smaller black hole revolves around it. The quasar OJ287 is visible due to the slow accretion of matter, present in the accretion disk, onto the largest black hole. Additionally, the small black hole passes through the accretion disk during its orbit which causes the disk material to heat up to very high temperatures. This heated material flows out from both sides of the accretion disk and radiates strongly for weeks. This causes peaks in the brightness, and the double peaks arise due to the ellipticity of the orbit, as shown in the figure.

The binary black hole model for OJ287 implies that the smaller black hole’s orbit should rotate, and this changes where and when the smaller hole impacts the accretion disk. This effect arises from Einstein’s General Theory of Relativity and its precessional rate depends mainly on the two black hole masses and the rotation rate of the more massive black hole. In 2010, Valtonen and collaborators used eight well timed bright outbursts of OJ287 to accurately measure the precession rate of the smaller hole’s orbit. This analysis revealed for the first time the rotation rate of the massive black hole along with accurate estimates for the masses of the two black holes. This was possible since the smaller black hole’s orbit precess at an incredible 39 degrees per individual orbit. The General Relativistic model for OJ287 also predicted that the next outburst could occur around the time of GR Centenary, 25 November 2015, which marks the 100th anniversary of Einstein’s General Theory of Relativity.

An observational campaign was therefore launched to catch this predicted outburst. The predicted optical flare began around November 18, 2015 and reached its maximum brightness on December 4, 2015. It is the timing of this bright outburst that allowed Valtonen and his co-workers to directly measure the rotation rate of the more massive black hole to be one third of the maximum spin rate allowed in General Relativity. In other words, its Kerr parameter is accurately measured to be 0.31 and its maximum allowed value in General Relativity is one. In comparison, the Kerr parameter of the final black hole associated with the first ever direct detection of gravitational waves is only estimated to be below 0.7.

The observations leading to accurate spin measurement have been made due to the collaboration of a number of optical telescopes in Japan, South Korea, India, Turkey, Greece, Finland, Poland, Germany, UK, Spain, USA and Mexico. The effort, led by Staszek Zola of Poland, involved close to 100 astronomers from these countries. Interestingly, a number of key participants were amateur astronomers who operate their own telescopes. Valtonen’s team that developed and contributed to the spinning binary black hole model include theoretical astrophysicist A. Gopakumar from TIFR, India, and Italian X-Ray astronomer Stefano Ciprini who obtained and analyzed the X-ray data.

The occurrence of the predicted optical outburst of OJ287 also allowed the team to confirm the loss of orbital energy to gravitational waves within two percent of General Relativity’s prediction. This provides the first indirect evidence for the existence of a massive spinning black hole binary emitting gravitational waves. This is encouraging news for the Pulsar Timing Array efforts that will directly detect gravitational waves from such systems in the near future. Therefore, the present optical outburst of OJ287 makes a fitting contribution to the centenary celebrations of General Relativity and adds to the excitement of the first direct observation of a transient gravitational wave signal by LIGO.

Mysterious Infrared Light From Space Resolved Perfectly

A research team using the Atacama Large Millimeter/submillimeter Array (ALMA) has detected the faintest millimeter-wave source ever observed. By accumulating millimeter-waves from faint objects like this throughout the Universe, the team finally determined that such objects are 100% responsible for the enigmatic infrared background light filling the Universe. By comparing these to optical and infrared images, the team found that 60% of them are faint galaxies, whereas the rest have no corresponding objects in optical/infrared wavelengths and their nature is still unknown.

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The Universe looks dark in the parts between stars and galaxies. However, astronomers have found that there is faint but uniform light, called the “cosmic background emission,” coming from all directions. This background emission consists of three main components; Cosmic Optical Background (COB), Cosmic Microwave Background (CMB), and Cosmic Infrared Background (CIB).

The origins of the first two have already been revealed. The COB comes from a huge number of stars, and the CMB comes from hot gas just after the Big Bang. However, the origin of the CIB was still to be solved. Various research projects, including past ALMA observations, have been conducted, but they could only explain half of the CIB.

A research team led by a graduate student, Seiji Fujimoto, and an associate professor, Masami Ouchi, at the University of Tokyo, tackled this mysterious infrared background by examining the ALMA data archive. ALMA is the perfect tool to investigate the source of the CIB thanks to its unprecedented sensitivity and resolution.

They went through the vast amount of ALMA data taken during about 900 days in total looking for faint objects. They also searched the datasets extensively for lensed sources, where huge gravity has magnified the source making even fainter objects visible.

“The origin of the CIB is a long-standing missing piece in the energy coming from the Universe,” said Seiji Fujimoto, now studying at the Institute of Cosmic Ray Research, the University of Tokyo. “We devoted ourselves to analyzing the gigantic ALMA data in order to find the missing piece.”

Finally, the team discovered 133 faint objects, including an object five times fainter than any other ever detected. The researchers found that the entire CIB can be explained by summing up the emissions from such objects (note).

What is the nature of those sources? By comparing the ALMA data with the data taken by the Hubble Space Telescope and the Subaru Telescope, the team found that 60% of them are galaxies which can also be seen in the optical/infrared images. Dust in galaxies absorbs optical and infrared light and re-emits the energy in longer millimeter waves which can be detected with ALMA.

“However, we have no idea what the rest of them are. I speculate that they are galaxies obscured by dust. Considering their darkness, they would be very low-mass galaxies.” Masami Ouchi explained passionately. “This means that such small galaxies contain great amounts of dust. That conflicts with our current understanding: small galaxies should contain small amounts of dust. Our results might indicate the existence of many unexpected objects in the distant Universe. We are eager to unmask these new enigmatic sources with future ALMA observations.”

Note: ALMA detected a part of the CIB with 1 mm wavelengths. The CIB in millimeter and submillimeter waves does not become weak even if the source is located far away. Therefore this wavelength is suitable for looking through the Universe to the most distant parts.