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.
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. VASIMR. Credit: Ad Astra
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.
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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).
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.
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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.
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.
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.
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.
On Wednesday, Oct. 7, there will be an historic first at the US president’s home: a star party. From a White House press release:
“The President and First Lady will host an event at the White House for middle-school students to highlight the President’s commitment to science, engineering and math education as the foundation of this nation’s global technological and economic leadership and to express his support for astronomy in particular – for its capacity to promote a greater awareness of our place in the universe, expand human knowledge, and inspire the next generation by showing them the beauty and mysteries of the night sky.”
About 20 telescopes will be set up on the White House lawn focused on Jupiter, the Moon and select stars, and supporters of the International Year of Astronomy are encouraged to follow this event, and host their own star parties to follow the example set.
There will also be interactive dome presentations, and hands-on activities including scale models of the Solar System, impact cratering, and investigating meteorites and Moon rocks. If haven’t been invited, you can participate by watching on NASA TV, or streaming on the White House website, starting at about 8 p.m. EDT. Even if clouds or rain intervene to prevent telescopic viewing, attendees will still have plenty to do.
The White House Star Party is just one of many family-friendly astronomy events and activities happening this fall. Among the others:
Ripples in Saturn's F ring. Credit: NASA/JPL/Space Science Institute
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Two shepherding moons continue to affect Saturn’s F ring in this amazing image captured by Cassini. Pandora on the outside of the ring and Prometheus on the inside, periodically create what are called “streamer-channels,” seen here in the F ring. The potato-shaped Prometheus pulls a streamer of material from the ring and leaves behind a dark channel. During its 14.7-hour orbit of Saturn, Prometheus (102 kilometers, or 63 miles across) reaches the point in its elliptical path, called apoapse, where it is farthest away from Saturn and closest to the F ring, and the moon’s gravity is just strong enough to draw a “streamer” of material out of the core region of the F ring.
The creation of such streamers and channels occurs in a cycle that repeats each Prometheus orbit: when Prometheus again reaches apoapse, it draws another streamer of material from the F ring. But since Prometheus orbits faster than the material in the ring, this new streamer is pulled from a different location in the ring about 3.2 degrees (in longitude) ahead of the previous one.
In this way, a whole series of streamer-channels is created along the F ring. In some observations, 10 to 15 streamer-channels can easily be seen in the F ring at one time.
This view looks toward the northern, sunlit side of the rings from about 10 degrees above the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Aug. 20, 2009. The view was obtained at a distance of approximately 2.3 million kilometers (1.4 million miles) from Saturn. Image scale is 13 kilometers (8 miles) per pixel.
This week’s Carnival of Space is over at Weird Warp.
Click here to read the Carnival of Space #123.
And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, let Fraser know if you can be a host, and he’ll schedule you into the calendar.
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