Universe Today

October 6, 2009December 24, 2015 by Nancy Atkinson

New Evidence of Seasonal Change on Titan

Stereographic projection of Synthetic Aperture Radar (SAR) imagery of Titan’s south polar region obtained between Sep. 2005 and July 2009. The Cassini radar has observed 60% of this area and 9% has repeat coverage. Areas where changes have been detected are outlined in red. Credit: Alex Hayes and Jonathan Lunine

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New images of Titan’s surface from the Cassini spacecraft show changes which are evidence of seasonal change. Objects identified earlier as liquid hydrocarbon lakes are shrinking and disappearing over the course of one to several Earth years. Scientists say seasonal temperature variations causing evaporation is the most likely cause for the changes observed. Cassini’s Synthetic Aperture Radar (SAR) repeatedly peered through Titan’s thick atmosphere, and data show that the lakes exhibit more than an order of magnitude increase in radar return and have disappearing borders between observations, suggesting surface change. These changes cannot be explained without invoking temporal variability, scientists reported at the American Astronomical Society’s Division for Planetary Sciences meeting now under way in Fajardo, Puerto Rico.

Alex Hayes, of the California Institute of Technology, and Dr. Jonathan Lunine, of the University of Rome Tor Vergata shared images of several regions on Titan’s south pole. Ontario Lacus is the largest and best characterized lake on Titan. Between July 2004 and July 2009, the shorelines of Ontario Lacus have receded, consistent with liquid evaporation and/or infiltration. In June and July 2009, the Cassini radar acquired its first high-resolution SAR images of the lake. Together with closest approach altimetry acquired in December 2008, these observations provide a unique opportunity to study Ontario.

Areas where the Cassini radar has observed transient surface liquid in Titan’s south polar region. The top two images are located near (60S, 210W) and were obtained in December 2007 and May 2009. Empty lake features are outlined in red and filled lakes, observed in the 2007 image, are outlined in cyan. The lake features disappear between observations. The bottom row consists of images near (69S, 90W) obtained in Oct. 2007 and Dec. 2008. Empty lake features observed in Dec. 2008 are outlined in red. The empty lake features in the bottom-left section of the image are dark in Oct. 2007, consistent with liquid-filled lakes. In the Dec. 2008 image the brightness of these features are indistinguishable from the empty lakes in the upper-right section of the image (which are bright in both observations), suggesting surface change.

Evaporation is the most likely scenario for observed changes on Titan’s surface. Alternative explanations include freezing, cryovolcanism, and subsurface infiltration. Freezing is unlikely due to thermodynamic reasons during the summer season in Titan’s south pole, and there are no clearly observable cryovolcanic features in the study areas. However, liquids evaporating and becoming part of a static hydrologic system is inconsistent with the observations. But, the scientists said, infiltration into a dynamic hydrologic system with a regionally varying methane/ethane table is possible.

“If evaporation is responsible, model results suggest rates are about 1m/yr, similar to current GCM estimates of methane evaporation rates for the latitudes and season in question,” Hayes and Lunine wrote in their press release. “An analysis of the receding shorelines observed in Ontario Lacus also yield evaporation rates of about 1 m/yr and support the results of the two- layer model for the smaller lakes. These observations constrain volatile fluxes and hence, the evolution of Titan’s hydrologic system.”

Source: AAS Planetary Science Division

October 6, 2009 by Nancy Atkinson

Arctic Sea Ice Extent is Third Lowest on Record

U.S. satellite measurements show Arctic sea ice extent in 2009 – the area of the Arctic Ocean covered by floating ice – was the third lowest since satellite measurements were first made in 1979. While the ice area at minimum was an increase from the past two years, it is still well below the average for the past 30 years. In the video above, Tom Wagner, NASA’s cryosphere program manager, describes the shrinking of Arctic sea ice and the significance of the problem for the rest of the planet.
Continue reading “Arctic Sea Ice Extent is Third Lowest on Record”

October 6, 2009December 24, 2015 by Nancy Atkinson

Two Black Holes Play a Little One on One

NGC 6240. Image credit: X-ray: NASA/CXC/MIT/ C.Canizares, M.Nowak; Optical: NASA/STScI

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If black holes could communicate, there would likely be a lotta in your face trash talkin’ going on between these two merging black holes. This image of NGC 6240 contains new X-ray data from Chandra (shown in red, orange, and yellow) that has been combined with an optical image from the Hubble Space Telescope originally released in 2008. The two black holes are a mere 3,000 light years apart and are seen as the bright point-like sources in the middle of the image.

Scientists think these black holes are in such close proximity because they are in the midst of spiraling toward each other – a process that began about 30 million years ago. It is estimated that the two black holes will eventually drift together and merge into a larger black hole some tens or hundreds of millions of years from now.

Finding and studying merging black holes has become a very active field of research in astrophysics. Since 2002, there has been intense interest in follow-up observations of NGC 6240 by Chandra and other telescopes, as well as a search for similar systems. Understanding what happens when these exotic objects interact with one another remains an intriguing question for scientists.

The formation of multiple systems of supermassive black holes should be common in the Universe, since many galaxies undergo collisions and mergers with other galaxies, most of which contain supermassive black holes. It is thought that pairs of massive black holes can explain some of the unusual behavior seen by rapidly growing supermassive black holes, such as the distortion and bending seen in the powerful jets they produce. Also, pairs of massive black holes in the process of merging are expected to be the most powerful sources of gravitational waves in the Universe.

Click here for access to larger versions of this image.

Source: Marshall Space Flight Center

October 6, 2009December 24, 2015 by Fraser Cain

Earth’s Layers For Kids

My son recently came back from a science day camp with one of the coolest things. It was a model of the Earth that he had created out of modeling clay. It showed the internal structure of the Earth, and because he built it, he was able to remember all of the layers of the Earth. Very cool. So here’s a good way to learn the Earth layers for kids.

To make your own, you need some modeling clay of different colors. You start by making a ball about 1.2 cm across. This represents the Earth’s inner core. Then you make a second ball about 3 cm across. This ball represents the Earth’s outer core. Then you make a third ball about 6 cm across. This ball represents the Earth’s mantle. And finally, you make some flattened pieces of clay that will be the Earth’s crust. To make it extra realistic, make some pieces blue and others green.

Take inner core and surround it with the outer core, and then surround that by the mantle. Cover the entire mantle with a thin layer of blue, and then put on some green continents on top of the blue.

If you’ve been really careful, you should be able to take a sharp knife and slice your Earth ball in half. You should be able to see the Earth’s layers inside, just like you’d see the real Earth’s layers. And you can see that the mantle is thicker underneath the Earth’s continents than it is under the oceans.

Here’s a link with more information from Purdue University so you can do the experiment yourself.

If you’re interested in teaching your children Earth science, here’s lots of information about volcanoes for kids.

We have also recorded a whole episode of Astronomy Cast just about Earth. Listen here, Episode 51: Earth.

October 6, 2009December 24, 2015 by Nancy Atkinson

Trips to Mars in 39 Days

Artist rendering of the VASIMR powered spacecraft heading to Mars. Credit: Ad Astra

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Using traditional chemical rockets, a trip to Mars – at quickest — lasts 6 months. But a new rocket tested successfully last week could potentially cut down travel time to the Red Planet to just 39 days. The Ad Astra Rocket Company tested a plasma rocket called the VASIMR VX-200 engine, which ran at 201 kilowatts in a vacuum chamber, passing the 200-kilowatt mark for the first time. “It’s the most powerful plasma rocket in the world right now,” says Franklin Chang-Diaz, former NASA astronaut and CEO of Ad Astra. The company has also signed an agreement with NASA to test a 200-kilowatt VASIMR engine on the International Space Station in 2013.

The tests on the ISS would provide periodic boosts to the space station, which gradually drops in altitude due to atmospheric drag. ISS boosts are currently provided by spacecraft with conventional thrusters, which consume about 7.5 tons of propellant per year. By cutting this amount down to 0.3 tons, Chang-Diaz estimates that VASIMR could save NASA millions of dollars per year.

The test last week was the first time that a small-scale prototype of the company’s VASIMR (Variable Specific Impulse Magnetoplasma Rocket) rocket engine has been demonstrated at full power.

Plasma, or ion engines uses radio waves to heat gases such as hydrogen, argon, and neon, creating hot plasma. Magnetic fields force the charged plasma out the back of the engine, producing thrust in the opposite direction.

They provide much less thrust at a given moment than do chemical rockets, which means they can’t break free of the Earth’s gravity on their own. Plus, ion engines only work in a vacuum. But once in space, they can give a continuous push for years, like wind pushing a sailboat, accelerating gradually until the vehicle is moving faster than chemical rockets. They only produce a pound of thrust, but in space that’s enough to move 2 tons of cargo.

Due to the high velocity that is possible, less fuel is required than in conventional engines.

Currently, the Dawn spacecraft, on its way to the asteroids Ceres and Vesta, uses ion propulsion, which will enable it to orbit Vesta, then leave and head to Ceres. This isn’t possible with conventional rockets. Additionally, in space ion engines have a velocity ten times that of chemical rockets.

Specfic impulse and thrust graph. Credit: NASA

Rocket thrust is measured in Newtons (1 Newton is about 1/4 pound). Specific impulse is a way to describe the efficiency of rocket engines, and is measured in time (seconds). It represents the impulse (change in momentum) per unit of propellant. The higher the specific impulse, the less propellant is needed to gain a given amount of momentum.

Dawn’s engines have a specific impulse of 3100 seconds and a thrust of 90 mNewtons. A chemical rocket on a spacecraft might have a thrust of up to 500 Newtons, and a specific impulse of less than 1000 seconds.

The VASIMR has 4 Newtons of thrust (0.9 pounds) with a specific impulse of about 6,000 seconds.

The VASIMR has two additional important features that distinguish it from other plasma propulsion systems. It has the ability to vary the exhaust parameters (thrust and specific impulse) in order to optimally match mission requirements. This results in the lowest trip time with the highest payload for a given fuel load.

In addition, VASIMR has no physical electrodes in contact with the plasma, prolonging the engine’s lifetime and enabling a higher power density than in other designs.

To make a trip to Mars in 39 days, a 10- to 20-megawatt VASIMR engine ion engine would need to be coupled with nuclear power to dramatically shorten human transit times between planets. The shorter the trip, the less time astronauts would be exposed to space radiation, and a microgravity environment, both of which are significant hurdles for Mars missions.

The engine would work by firing continuously during the first half of the flight to accelerate, then turning to deaccelerate the spacecraft for the second half. In addition, VASIMR could permit an abort to Earth if problems developed during the early phases of the mission, a capability not available to conventional engines.

VASIMR could also be adapted to handle the high payloads of robotic missions, and propel cargo missions with a very large payload mass fraction. Trip times and payload mass are major limitations of conventional and nuclear thermal rockets because of their inherently low specific impulse.

Chang-Diaz has been working on the development of the VASIMR concept since 1979, before founding Ad Astra in 2005 to further develop the project.

Source: PhysOrg

October 6, 2009December 24, 2015 by Fraser Cain

How Big is Earth?

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Here’s a question: how big is Earth? Let’s take a look at how big our planet is.

First, the equatorial diameter of Earth is 12,756 km. In other words, if you dug a tunnel on the equator that went straight down and went right through the center of the Earth, it would be about 12,756 km long. Just for comparison, that’s about 1.9 times the diameter of Mars. And only .09% the diameter of Jupiter.

The volume of Earth is 1.08 x 10¹² km³. Written another way, that’s 1.08 trillion cubic kilometers of rock and metal. Again, it’s about 6.6 times more volume than Mars.

The surface area of Earth is 510,072,000 square kilometers. Of that, 29.2% is covered by land and 70.8% is covered by water. Just for comparison, that’s 3.5 times as much surface area as Mars.

The mass of Earth is 5.97 x 10²⁴ kg. Here that is written out: 5,970,000,000,000,000,000,000,000 kg. Yeah, that’s a really big number. And yet, it’s only 0.3% the mass of Jupiter (and Jupiter is mostly lightweight hydrogen).

We have written many articles about Earth for Universe Today. Here’s an article about how fast Earth rotates, and here’s an article about Earth’s magnetic field.

You can learn more about Earth from NASA’s Earth Observatory, as well as NASA’s Solar System Exploration Guide.

We have also recorded an entire episode of Astronomy Cast that’s just about Earth. Listen here, Episode 51: Earth.

October 6, 2009December 24, 2015 by Nancy Atkinson

Your CCD Camera Just Won a Nobel Prize

Charged Coupled Devices (CCD) for Ultra-Violet and Visible Detection. Credit: NASA

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Well, actually, the people who invented the first successful imaging technology using a digital sensor, called a CCD (Charge-Coupled Device), have been awarded the Nobel Prize in Physics. In 1969 Willard S. Boyle and George E. Smith came up with the idea “from their own heads,” Smith said, and CCDs revolutionized photography, as light could now be captured electronically instead of on film, and became an irreplaceable tool in astronomy, providing new possibilities to visualize the previously unseen. The device also made it possible for amateur astronomers to rival the professionals in terms of quality astrophotography. CCD technology is also used in many medical applications, e.g. imaging the inside of the human body, both for diagnostics and for microsurgery. Sharing the prize with Boyle and Smith is Charles K. Kao, who in 1966 made a discovery that led to a breakthrough in fiber optics.

Both achievements helped shape the foundations of today’s networked societies.

October 6, 2009December 24, 2015 by Nancy Atkinson

NASA Astronaut Dies

Astronaut Frank Caldeiro, 1958-2009. Credit: NASA

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NASA astronaut Fernando “Frank” Caldeiro died Saturday morning after a two and a half year battle with brain cancer. Although he never flew in space, Caldeiro served as the lead astronaut in several technical support roles. “Frank was a valued member of the astronaut corps and the Flight Crew Operations team,” said Brent Jett, director, Flight Crew Operations. “He provided a wealth of experience and made significant contributions to the success of both the WB-57 project and the Space Shuttle Program. He will be missed by all those who knew him at NASA. Our hearts go out to his family.” Caldeiro was 51.

More on Caldeiro:

He was the first person of Argentinean descent to train for a space flight. Caldeiro joined NASA’s Kennedy Space Center, Fla., in 1991 as a cryogenics and propulsion systems expert for the safety and mission assurance office, he took part in 52 space shuttle launches before being selected as an astronaut in 1996.

He served as the lead astronaut for the station’s life support systems and its European-built components, reviewing the design and manufacture of the U.S. “Harmony” Node 2 and European Space Agency (ESA) Columbus modules, as well as the yet-to-be-launched Cupola robotics viewing port and the space shuttle-lofted cargo carriers, the Multi Purpose Logistics Modules (MPLM).

From June 2005 to December 2006, Caldeiro served as the lead astronaut in charge of shuttle software testing at the Johnson Space Center’s Shuttle Avionics Integration Laboratory, testing in-flight maintenance procedures, prior to being reassigned to Houston’s nearby Ellington Field to direct the high-altitude atmospheric research experiment program carried onboard NASA’s WB-57 aircraft. He was still serving in that role when he passed away.

Caldeiro however, would never be assigned to a mission.

In 2006, he told the Orlando Sentinel, “Flying in space, to me, has become more like, well, you know, you can’t chase something so much that you run it over. You can be obsessed by it and be miserable or you can say, ‘Well, this is an opportunity; I’m first in line in front of 350-million other people.'”

His family migrated to the US from Argentina when Caldeiro was 16. He didn’t speak any English at that time, but went on to complete a Master of Science degree in engineering management from the University of Central Florida. In 2002, he was named National Hispanic Scientist of the Year by the Museum of Science and Industry in Tampa, Florida. That same year, he was appointed by President George W. Bush to serve on the Advisory Commission on Educational Excellence for Hispanic Americans under the “No Child Left Behind” Act.

He is survived by his wife and two daughters.

Sources: NASA, collectSPACE

October 5, 2009April 26, 2016 by Nancy Atkinson

Understanding 2008 TC3 a Year After Impact

Discovery images of asteroid 2008 TC3, as it was seen on October 6, 2008, by the Catalina Sky Survey at Mount Lemmon in Arizona (Richard Kowalski).

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The first asteroid to have been spotted before hitting Earth, 2008 TC3, crashed in northern Sudan one year ago on October 6. Several astronomers have been trying to piece together a profile of this asteroid, pulling together information from meteorites found at the impact site and the images captured of the object in the hours before it crashed to Earth.

“We have a gigantic jigsaw puzzle on our hands, from which we try to create a picture of the asteroid and its origins,” said SETI Institute astronomer Peter Jenniskens, who worked at the crash site, “and now we have with a composite sketch of the culprit, cleverly using the eyewitness accounts of astronomers that saw the asteroid sneak up on us.” Their description? 2008 TC3 looked like a loaf of walnut-raisin bread.

“The asteroid now has a face,” said Jenniskens, chair of the special session at the fall meeting for the Division for Planetary Sciences of the American Astronomical Society. Last December, Jenniskens and Sudan astronomer Muawia Shaddad went to the crash site and recovered 300 fragments in the Nubian Desert. Like detectives, students from the University of Khartoum helped sweep the desert to look for remains of the asteroid. They found many different-looking meteorites close to, but a little south, of the calculated impact trajectory.

The team has also been able to recreate the shape of the asteroid from looking at images captured by Astronomers Marek Kozubal and Ron Dantowitz of the Clay Center Observatory in Brookline, Massachusetts, who tracked the asteroid with a telescope and captured the flicker of light during a two hour period just before impact.

An irregular shape and rapid tumbling caused asteroid 2008 TC3 to flicker when it reflected sunlight on approach to Earth.

Peter Scheirich and colleagues at Ondrejov Observatory and Charles University in the Czech Republic combined all the various observations to work out the shape and orientation of the asteroid.

Watch a video recreation of 2008 TC3 tumbling in space.

Larger version. (1.32 MB Mpeg 4 file)

Video of 2008 TC3 as seen through a telescope (large file, 7.63 MB)

Other forensic evidence based on analysis of the recovered meteorites at the Almahata Sitta site showed the asteroid was an unusual “polymict ureilite” type. Jason S. Herrin of NASA’s Johnson Space Center confirmed that the meteorites still carry traces of being heated to 1150-1300 degrees C, before rapidly cooling down at a rate of tens of degrees C per hour, during which carbon in the asteroid turned part of the olivine mineral iron into metallic iron. Hence, asteroid 2008 TC3 is the remains of a minor planet that endured massive collisions billions of years ago, melting some of the minerals, but not all, before a final collision shattered the planet into asteroids.

Mike Zolensky of NASA’s Johnson Space Center first pointed out that, as far as ureilites are concerned, his meteorite is unusually rich in pores, with pore walls coated by crystals of the mineral olivine. He now reports, from X-ray tomography work with Jon Friedrich of Fordham University in New York, that those pores appear to outline grains that have been incompletely welded together and that the pore linings appear to be vapor phase deposits. According to Zolensky, “Almahata Sitta may represent an agglomeration of coarse- to fine-grained, incompletely reduced pellets formed during impact, and subsequently welded together at high temperature.”

The carbon in the recovered meteorites is among the most cooked of all known meteorites. Carbon crystals of graphite and nanodiamonds have been detected. Still, it turns out that some of the organic matter in the original material survived the heating. Amy Morrow, Hassan Sabbah, and Richard Zare of Stanford University have found polycyclic aromatic hydrocarbons in high abundances. Amazingly, Michael Callahan and colleagues of NASA’s Goddard Space Flight Center now report that even some amino acids have survived.

Jenniskens and Shaddad plan to revisit the scene of the crash in the Nubian Desert. They reported their findings at the Division for Planetary Sciences of the American Astronomical Society meeting in Puerto Rico.

Listen to Oct. 6th’s 365 Days of Astronomy podcast by Emily Lakdawalla about 2008 TC3.

Source: AAS Planetary Science Division

October 5, 2009December 24, 2015 by Nancy Atkinson

Massive Mosaic of Mercury

Mosaic of Mercury. Credit: NASA / JHUAPL / CIW / mosaic by Jason Perry

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If you want to REALLY see Mercury up close and personal, take a look at this absolutely HUGE mosaic of the planet. It was put together by Jason Perry, who actually works with the Cassini mission but in his spare time stitched together 66 images from the MDIS narrow angle camera from the MESSENGER mission’s second flyby of Mercury in October 2008, along with some data from the Mariner 10 mission in the 1970’s. The full file is 20 MB, with a resolution of 0.6 kilometers (0.37 miles) per pixel. What fun! —for us, that is. It took Perry four days just to set up his software, according to Emily Lakdawalla at the Planetary Society Blog.

Enjoy!