ESA Rosetta Comet 67/P Mission: Rosetta Team Uncovers More Secrets

A colour image of Comet 67P/Churyumov-Gerasimenko composed of three images taken by Rosetta’s scientific imaging system OSIRIS in the red, green and blue filters; the images were taken on August 6, 2014 from a distance of 120 km from the comet. 

Image credit: ESA / Rosetta / MPS / OSIRIS Team / UPD /LAM / IAA / SSO / INTA / UPM / DASP / IDA.

The familiar shape of the comet has now had many of its vital statistics measured: the small lobe measures 2.6 × 2.3 × 1.8 km and the large lobe 4.1 × 3.3 × 1.8 km.

The total volume of the comet is 21.4 km3. Rosetta’s Radio Science Instrument has measured its mass to be 10 billion tons, yielding a density of 470 kg/m3.

By assuming an overall composition dominated by water ice and dust with a density of 1,500–2,000 kg/m3, Rosetta scientists show that the comet has a very high porosity of 70–80 percent, with the interior structure likely comprising weakly bonded ice-dust clumps with small void spaces between them.

The OSIRIS instrument has imaged some 70 percent of the surface to date: the remaining unseen area lies in the southern hemisphere that has not yet been fully illuminated since Rosetta’s arrival.

The scientists have so far identified 19 regions separated by distinct boundaries and, following the ancient Egyptian theme of the Rosetta mission, these regions are named for Egyptian deities, and are grouped according to the type of terrain dominant within.

The 19 regions identified on 67P/Churyumov–Gerasimenko are separated by distinct geomorphological boundaries; they are grouped according to the type of terrain dominant within each region. 

Five basic categories of terrain type have been determined: dust-covered (Ma’at, Ash and Babi); brittle materials with pits and circular structures (Seth); large-scale depressions (Hatmehit, Nut and Aten); smooth terrains (Hapi, Imhotep and Anubis), and exposed, more consolidated surfaces (Maftet, Bastet, Serqet, Hathor, Anuket, Khepry, Aker, Atum and Apis). 

Image credit: ESA / Rosetta / MPS / OSIRIS Team / UPD /LAM / IAA / SSO / INTA / UPM / DASP / IDA.

Five basic, but diverse, categories of terrain type have been determined: dust-covered; brittle materials with pits and circular structures; large-scale depressions; smooth terrains; and exposed more consolidated surfaces.

Much of the northern hemisphere is covered in dust. As the comet is heated, ice turns directly into gas that escapes to form the atmosphere or coma.

Dust is dragged along with the gas at slower speeds, and particles that are not traveling fast enough to overcome the weak gravity fall back to the surface instead.

Some sources of discrete jets of activity have also been identified. While a significant proportion of activity emanates from the smooth neck region, jets have also been spotted rising from pits.

The gases that escape from the surface have also been seen to play an important role in transporting dust across the surface, producing dune-like ripples, and boulders with ‘wind-tails,’ the boulders act as natural obstacles to the direction of the gas flow, creating streaks of material ‘downwind’ of them.

“Because comets have very little gravity, dust and gas flow freely into space. But we were surprised to find a cloud of particles orbiting the comet that are large and heavy enough to defy the Sun’s radiation pressure,” said Dr Dennis Bodewits of the University of Maryland.

The scientists were able to make this discovery thanks to OSIRIS’ very sensitive cameras.

“Each pixel is about 30 cm. You couldn’t see a coffee cup, but you could see a large lunchbox. The resolution is about 10 times higher than Google Earth.”

According to the team, 67P/Churyumov-Gerasimenko was releasing the earthly equivalent of 1.2 liters of water into space every second at the end of August 2014.

MIRO (Microwave Instrument for the Rosetta Orbiter)

Credit: ESA

“In observations, made by the Microwave Instrument for Rosetta Orbiter (MIRO), over a period of three months, the amount of water in vapor form that the comet was dumping into space grew about tenfold,” said Dr Sam Gulkis of NASA’s Jet Propulsion Laboratory in Pasadena.

“To be up close and personal with a comet for an extended period of time has provided us with an unprecedented opportunity to see how comets transform from cold, icy bodies to active objects spewing out gas and dust as they get closer to the Sun.”

NASA and NOAA help reveal melt secrets of Great Lakes ice

A colour-coded image of major ice types on Lake Superior, made from a RADARSAT1 radar backscatter image using a new NASA and NOAA-developed technique. 

Credit: NOAA Great Lakes Environmental Research Laboratory and NASA/JPL-Caltech

Two scientists from NASA and NOAA have developed a new space-based technique for monitoring the ice cover of the Great Lakes that is so accurate it can identify a narrow channel of open water cut through the ice by an icebreaker—even at night.

"In the dark, it's difficult to read a map that's right in front of you," said Son Nghiem of NASA's Jet Propulsion Laboratory, Pasadena, Calif., one of the developers of the new technique.

Son Nghiem

"Yet we now have a way to use satellite radars almost 500 miles [800 kilometers] out in space to see through clouds and darkness and map ice across the Great Lakes."

Ice on the Great Lakes puts a big chill on the U.S. and Canadian economies, affecting shipping, fishing and also public safety when winter and spring flooding are caused by ice jams.

It has a significant impact on the regional environment and ecological systems as well. Yet previous techniques of analyzing satellite observations of the ice sometimes misidentified ice as water and vice versa.

The new method, co-developed by Nghiem and his colleague George Leshkevich of NOAA's Great Lakes Environmental Research Laboratory, Ann Arbor, Mich., not only corrects that problem, it also gives a more accurate analysis of ice characteristics, such as whether the ice is dense or full of bubbles, and whether it has melted and refrozen.

Leshkevich said the method has now been transitioned to NOAA for routine use in generating ice maps across the Great Lakes.

"These maps will provide important information for environmental management, ice forecasting and modeling, off-shore wind farm development, operational icebreaking activities in support of winter navigation, and science research."

The more accurate classification of ice will also be useful for scientific research into such questions as how the Great Lakes are responding to, and leading, climate change in the upper Midwest.

More information: www.iaglr.org/jglr/release/39/2013.05.003_leshkevich.php

Obese Black-Hole Galaxies Could Reveal Quasar Secrets

Obese black-hole galaxies could be a stepping stone to the quasars we see today. 

CREDIT: NASA/ESA 

Gluttonous black holes in the center of some galaxies could be precursors to the brightest objects in the known universe.

A recently proposed type of galaxy with an overwhelmingly large black hole in its center could give astronomers a better understanding of the formation of quasars — bright objects in galaxies with supe-rmassive black holes.

The centers of these obese black-hole galaxies (OBGs) could harbour black holes so massive that radiation from where the black hole accretes would overwhelm that of the stars within its galaxy.

New research indicates that some of the most luminous quasars seen from Earth were likely OBGs first before something "lit up" the black hole and had it pump out energy visible from Earth.

The simulations indicate there could be a million OBGs in the observable universe, making the team behind the work ask, why don't we see them?

Tanking up
The team, led by scientists from the Max Planck Institute for Extraterrestrial Physics in Germany, was trying to figure out why astronomers can see quasars from a very far away, at the beginning of the universe. (More distant objects are older and have less metal in them.)

"People have hypothesized there could be these black holes forming from this metal-free gas reservoir ... which is completely free of stars," said Bhaskar Agarwal, a doctoral research fellow at Max Planck who led the research.

This means the black holes in OBGs could have formed separately from the stars surrounding them, contradicting recent observations by the Herschel Space Observatory.

In that earlier finding, astronomers suggested that galaxies that have black holes in their center — including the Milky Way — see the stars and black holes evolve together.

Other research, including observational research, also shows OBG-like objects with a very massive black hole at the center of the galaxy, Agarwal told reporters.

But if the black holes in OBGs formed solo from a reservoir of gas, the stars must have come from somewhere.

The simulations suggested the black hole would have remained on its own until a merger between galaxies brought stars within its vicinity.

The results were published in the Monthly Notices of the Royal Astronomical Society by Oxford University Press on May 29.

Participating researchers came from Max Planck, Yale University and the University of Edinburgh.

NASA's Juno Mission: Probe to Examine Jupiter's Biggest Secrets

Jupiter is probably the best place in the solar system to study how the magnetic fields of planets are generated. 

The Juno spacecraft will make the five-year, 400-million-mile voyage to Jupiter and orbit the planet, collecting data for more than one Earth year.

CREDIT: NASA/JPL-Caltech

A NASA probe that is traveling through space on its way to Jupiter is expected to help astronomers unlock mysteries about the largest planet in our solar system when it arrives there in 2016.

NASA's Juno mission was launched in August 2011 to study how Jupiter formed and evolved. After a five-year journey, the spacecraft is expected to arrive at the gas giant planet in August 2016.

Jupiter has long intrigued astronomers, from the planet's distinct surface features and complex weather systems to its mysterious origin and evolution, said Fran Bagenal, a professor of astrophysical and planetary sciences at the University of Colorado in Boulder, and a co-investigator on the Juno mission.

"People have been looking at this exterior since the time of Galileo," she said. "[But] we know very little of what's inside. We're sending Juno out there to Jupiter to try to understand the origin and evolution of Jupiter, [to] try to explain how much water there is, what it's like inside, what the atmosphere is like."

Bagenal discussed the exciting results the Juno mission is expected to yield in a session on June 11 here at the 220th meeting of the American Astronomical Society.

Once the solar-powered Juno spacecraft is captured into orbit around Jupiter, the probe will map the planet's magnetic and gravitational fields to learn more about the interior structure of Jupiter.

[Photos: NASA's Juno Mission to Jupiter]

Secrets of Supermassive Black Holes Revealed

These images, taken with the 2.1-meter telescope at Kitt Peak National Observatory in Arizona, show galaxy shapes that are either physically intertwined or distorted by the gravity of nearby neighbors.

These AGN were known prior to the Swift survey, but Swift has found dozens of new ones in more distant galaxies. Credit:

NASA/Swift/NOAO/Michael Koss and Richard Mushotzky (Univ. of Maryland)

Researchers had scratched their heads over why such high-energy displays occurred, until now. The findings announced today confirm past theories that suggested that violence from galactic mergers can fuel the growth of central black holes.

"We find that about 25 percent of black holes found by Swift are in the process of merging," said team member Michael Koss of the University of Maryland in College Park, during a NASA teleconference.

About 60 percent of such active galaxies will merge completely within the next billion years to create giant black holes.

Hard X-ray action

Swift used its Burst Alert Telescope (BAT) to detect any telltale signs of hard X-rays, which rank between gamma-rays and X-rays on the electromagnetic spectrum of light.

Such hard X-rays can pass through interstellar gas or dust which otherwise blocks ultraviolet, optical and soft-X-ray light. Infrared radiation can also pass through the material, but may represent emissions from a galaxy's star nurseries rather than the central black holes.

The hard X-ray survey allowed astronomers to feel confident that they had spotted the majority of AGN within Swift's survey range of about 650 million light-years away. (A light-year is the distance that light can travel in one year — about 6 trillion miles (10 trillion km).)

Koss and his colleagues then followed up by spending 20 nights peering at the AGN with a 2-meter telescope at Kitt Peak National Observatory near Tucson, Ariz.

"Many of these galaxies are very close to us, so we see the severe distortion of the galaxy shapes," Koss explained. "In addition, we see that the galaxies are very close to each other and therefore will merge and interact very strongly."

Like good neighbours do!

The Secrets Inside Your Dog's Mind

The Secrets Inside Your Dog's Mind

Henry the schnoodle just did a remarkable thing. Understanding a pointed finger may seem easy, but consider this: while humans and canines can do it naturally, no other known species in the animal kingdom can. Consider too all the mental work that goes into figuring out what a pointed finger means: paying close attention to a person, recognising that a gesture reflects a thought, that another animal can even have a thought. Henry, as Kivell affectionately admits, may not be "the sharpest knife in the drawer," but compared to other animals, he's a true scholar.