Nancy Atkinson, Author at Universe Today

August 15, 2008December 24, 2015 by Nancy Atkinson

Astronomers Answer Your Questions About “Celestial Geode”

Hubble image of N44F, the Celestial Geode.

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Last week, we posted the image above as part of our “Where In The Universe” challenge, where we test our readers’ visual knowledge of our universe. This incredible and unusual Hubble image of object N44F, known as the “Celestial Geode” is a gas cavity carved by the stellar wind and intense ultraviolet radiation from a hot young star. Readers were fascinated by the object and wanted to know more. One of our regular readers, Jorge, asked this question about N44F: “Why is it that we see the back “wall” of the bubble, we see the side walls, but we don’t see the front wall?” I wasn’t able to answer that question, so I sought out one of the astronomers responsible for this image, Dr. You-Hua Chu, professor at the University of Illinois, Urbana-Champaign. Not only did Dr. Chu provide wonderful information about the image, but one of her former students, Dr. Rosie Chen provided Universe Today with an exclusive Spitzer Space Telescope image of the Celestial Geode that has never been published before on the internet.

Dr. Chu explained in more detail what we see in the Hubble image. “This picture shows a cluster of stars that were formed recently, maybe about a million years ago,” she said. “The entire geode was a dense ball of gas and dust. It collapsed under its own gravity to form the cluster of stars.”

Once some massive stars were formed, there was enough UV radiation to ionize the remaining gas, and the stellar wind blows the gas outward. “Depending on how much material exists in each direction,” said Dr. Chu, “an expanding blister may form in the direction with low densities, or a stalled wall is formed in the direction with high densities.”

In response to the question about why we don’t see the front wall of the bubble, Dr. Chu compared the Celestial Geode to a store’s display case. The front wall is so thin, it is as transparent as glass. “You might ask how come we are so lucky to be peering through the thinnest wall of this geode,” said Dr. Chu. “Well, if we were looking at the geode in directions where thick walls exist, we wouldn’t be able to see the inside.”

Dr. Chu said the walls are like a balloon with uneven thickness. The thinnest part will be inflated most and become transparent.

“The interesting thing about this geode is that along its dense wall there are dust pillars sticking out and young stars are being formed at the tips of these pillars. We have obtained Spitzer Space Telescope images of this region and find IR (infrared) sources at the tips of the pillars and the spectral properties of these IR sources suggest that they contain young stars that are still enshrouded in dust.” And here is the Spitzer color composite image, provided by Dr. Rosie Chen, a researcher at the University of Virginia, and created by Dr. Adeline Caulet:

Spitzer/Hubble color composite image of N44F. Credit: Dr. Adeline Caulet

Both Drs. Chu and Chen warned that the Spitzer image may be a bit of a disappointment after seeing the Hubble image. “As you can see the HST images show clearly the detail structure while the Spitzer image is more fuzzy,” said Dr. Chen. “This is because HST’s resolution is over 10 times better than Spitzer.”

When I asked Dr. Chu about how the Hubble image was obtained, she said it was somewhat an accident that this particular part of N44 was imaged. “I proposed to Hubble to observe the superbubble N44 because it had X-ray emissions and I wanted to use high-resolution images to search for supernova remnant shocks,” she said. “The observation was made, but not properly made, so I requested a make-up observation at a slightly different location in N44 to allow an arbitrary roll angle of the space craft.” The Celestial Geode was at the new central position. Dr. Chu said she chose that position because she had always been interested to see what was going on in the ionized gas region, but didn’t have a convincing excuse to propose an observation. “You can say that I took advantage of the make-up observation to sneak in this object,” she said.

In researching this article, I noticed Dr. Chu’s name associated with many outstanding astronomical images. I told her she must be a busy astronomer. “I have to say that I am a lucky astronomer,” she said. “I try to pursue truth and beauty at the same time.”

Chu and Chen’s paper on N44: “Chen, C.-H.R., and Chu, Y.-H. Gruendl, R.A., Gordon, K.D., and Heitsch, F., “Spitzer View of Young Massive Stars in the LMC HII Complex N44,” 2008, ApJ, submitted.”

August 15, 2008December 24, 2015 by Nancy Atkinson

GLAST Science Operations Underway: Now, About That Name!

Artists impression of GLAST in orbit. Credit: NASA

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After a 60-day checkout period, science operations have begun in earnest for GLAST, the Gamma ray Large Area Space Telescope, which is now surveying the gamma-ray sky. Launched on June 11, 2008, the GLAST spacecraft has been undergoing calibrations of the two instruments on board, the LAT (Large Area Telescope) and the GBM (GLAST Burst Monitor) — more details on the instruments in a moment. But during the checkout phase both instruments made significant observations of gamma rays. “Given that these detections were made with just the engineering data observations, the future is full of promise, and we are very excited,” said Dr. Steve Ritz, GLAST Project Scientist in his GLAST blog. At the end of August, there will be a formal release of the first-light images taken by the spacecraft. Also at that time, NASA will rename the observatory. I don’t know about you, but I’m sort of attached to the name “GLAST.” But it will be interesting to find out its new, official name.

In June, LAT detected two extraordinarily bright, flaring sources in space, which scientists believe are very likely supermassive black hole systems at the cores of active galaxies, located far across the universe, but incredibly bright. Additionally, by the end of July, the GBM had detected 12 gamma ray bursts.

“We are thrilled to be detecting gamma-ray bursts so early in the mission. GLAST and the GBM are off to a great start!” said Charles “Chip” Meegan, GBM principal investigator at NASA’s Marshall Space Flight Center, Huntsville, Ala. “The detectors are working well and we’re really pleased with how the instrument is working. That said, we’re using this checkout period to scrutinize the data coming down from the detectors and fine tune flight and ground software and our daily operational processes.”

The LAT detects gamma rays and is able to make gamma ray images of astronomical objects. The GBM is designed to observe gamma ray bursts, which are sudden, brief flashes of gamma rays that occur about once a day at random positions in the sky. The GBM has such a large field-of-view that it will be able to see bursts from over 2/3 of the sky at one time. The observations made by GBM were verified by the Swift Telescope, another space telescope that can swiftly skew around to view a gamma ray burst.

NASA has a tradition of renaming spacecraft after a successful launch, and with GLAST they decided to wait until the “first light” images are released. Any guesses on what the new name will be?

Source: GLAST blog

August 14, 2008December 24, 2015 by Nancy Atkinson

Cassini Pinpoints Source of Jets on Saturn’s Moon Enceladus

The Baghdad and Cairo Sulci, sources of geysers on Enceladus. Image: NASA/JPL/Space Science Institute

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Cassini scientists have been “bee-busy” poring over the images from the August 11 flyby of Saturn’s geyser-spewing moon Enceladus, says Carolyn Porco, the lead for the imaging team. And quickly, they have found exactly what they were looking for: Cassini has pinpointed precisely where the icy jets erupt from the moon’s geologically active moon surface. Enceladus. “This is the mother lode for us,” said Porco, “a place that may ultimately reveal just exactly what kind of environment — habitable or not — we have within this tortured little moon.”

New carefully targeted pictures reveal exquisite details in the prominent south polar “tiger stripe” fractures from which the jets emanate. The images show the fractures are about 300 meters (980 feet) deep, with V-shaped inner walls. The outer flanks of some of the fractures show extensive deposits of fine material. Finely fractured terrain littered with blocks of ice tens of meters in size and larger (the size of small houses) surround the fractures.

Damscus Sulcus, another source of geysers on Enceladus. Image: NASA/JPL/Space Science Institute

One highly anticipated result of this flyby was finding the location within the fractures from which the jets blast icy particles, water vapor and trace organics into space. Scientists are now studying the nature and intensity of this process on Enceladus, and its effects on surrounding terrain. This information, coupled with observations by Cassini’s other instruments, may answer the question of whether reservoirs of liquid water exist beneath the surface.

The high-resolution images were acquired as Cassini sped past the icy moon at 64,000 kilometers per hour (40,000 miles per hour). A special technique, dubbed “skeet shooting” by the imaging team, was developed to cancel out the high speed of the moon relative to Cassini and obtain the ultra-sharp views.

“Knowing exactly where to point, at just the right time, was critical to this event,” said Paul Helfenstein, Cassini imaging team associate at Cornell University, Ithaca, NY., who developed and used the skeet-shoot technique to design the image sequence. “The challenge is equivalent to trying to capture a sharp, unsmeared picture of a distant roadside billboard with a telephoto lens out the window of a speeding car.”

False color mosaic shows the south pole region where the jets emanate. Image: NASA/JPL/Space Science Institute

The tiger stripes, officially called sulci, have been named for characters and places from “The Arabian Nights.” The yellow circles on the images indicate the sources of the jets.

Helfenstein said that from Cassini’s point of view, “Enceladus was streaking across the sky so quickly that the spacecraft had no hope of tracking any feature on its surface. Our best option was to point the spacecraft far ahead of Enceladus, spin the spacecraft and camera as fast as possible in the direction of Enceladus’ predicted path, and let Enceladus overtake us at a time when we could match its motion across the sky, snapping images along the way.”

For scientists, having the combination of high-resolution snapshots and broader images showing the whole region is critical for understanding what may be powering the activity on Enceladus.

“There appears to have been extensive fallout of icy particles to the ground, along some of the fractures, even in areas that lie between two jet source locations, though any immediate effects of presently active jets are subtle,” said Porco.

Imaging scientists suggest that once warm vapor rises from underground to the cold surface through narrow channels, the icy particles may condense and seal off an active vent. New jets may then appear elsewhere along the same fracture.

“For the first time, we are beginning to understand how freshly erupted surface deposits differ from older deposits,” said Helfenstein, an icy moons expert. “Over geologic time, the eruptions have clearly moved up and down the lengths of the tiger stripes.”

News Source: NASA/JPL

August 14, 2008December 24, 2015 by Nancy Atkinson

Tyson and Sykes Duke Out the Great Planet Debate; Flatow Almost Flattened

A debate today between astronomer Neil deGrasse Tyson and planetary scientist Mark Sykes, moderated by NPR’s Ira Flatow, addressed the issue of Pluto’s planetary status. There was lots of arm-waving and finger-pointing, endless interruptions, disagreements on details big and small, and battling one-liners. The two scientists sat at a table with the moderator between them and Flatow was often obscured by Tyson and Sykes getting in each other’s faces in eye-to-eye confrontation. At one point, Flatow was hit by Tyson’s ebullient arm motions. Yes, it was heated. But it was fun, too. It ended up being not so much a debate between the Pluto-huggers and the Pluto-haters as a disagreement over the lexicon of astronomy and planetary science and, primarily, the definition of a planet. Pluto’s planetary status was definitely not decided here, and the debate concluded with an amicable agree-to-disagree concurrence that the scientific process is an ongoing, evolving practice. But it wasn’t without fireworks.

At the start of the Great Planet Debate, Flatow laid down the ground rules, which included no throwing of perishable items, but that was about the only rule that didn’t get disregarded. Tyson, director of the Hayden Planetarium in New York and host of Nova ScienceNow, and who is in the camp that Pluto is not a planet, began his opening statements with “It’s simple. The word ‘planet’ has lost all scientific value.” He went on, saying “planet” doesn’t tell you much and you have to ask all sorts of questions such as is it big or small, rocky or gaseous, in the habitable zone or not, etc. “If you have to ask twenty questions after I say I’ve discovered a planet, the word has lost its utility.” Tyson said “planet” had utility far back in time when there wasn’t much else we knew about, but we know so much more now. “If we’re going rely on one word and put them all in one pot, what are we doing as scientists and educators? The time has come to discard the useless words and invent a whole new system to respect the level of science we have achievedâ€¦We’re in desperate need of a new lexicon to accommodate this knowledge,” he said.

Sykes, director of the Planetary Science Institute, and who believes Pluto should be reinstated as a planet, began, “How we categorize things is part of the science process. It is natural for humans to group things together with common characteristics as a tool to better understand and how they work. This applies to biology and astronomy as well.” He continued that we have discovered planets around other stars and continue to find Kuiper Belt objects that will need to be classified, so classifying objects is not a useless task. The IAU (International Astronomical Union) bit the bullet and decided on a classification, but unfortunately, Sykes said, what they came up with was not very useful.

That was the end of decorum, as Tyson interrupted with, “You wanted a definition. They gave you a definition and now you’re complaining about it!”

“Absolutely,” said Sykes, wanting to continue, but Tyson quickly chimed in, “And let me addâ€¦”, where Sykes butted in with “You have to let me start before you add!”

Flatow looked around and said, “I think I’m in a danger zone here.”

Thus began the debate.

Sykes said that any definition has to have a reason, or a purpose. According to the IAU’s definition, planets have to orbit the sun, they have to be round, and they have to have cleared their orbits, among other things. There was immediate confusion with this definition, which Sykes said was a little “goofy.” In order to be a planet, an object has be bigger the farther away it is from the sun, and it ignores the physical characteristics. He believes it’s useful to group things together that are similar and then have subcategories. So, you have planets, under which are terrestrial, gas giants, ice planets, etc.

Tyson said that even for him, the IAU’s definition falls short of taking the total amount of information to task. “If you only want to call round things planets, that puts Pluto in the same class as Jupiter. I happen to like round things. But what other lexicon might be available to group similar things together?”

“That’s why god made subcategories,” said Sykes. “It’s good to have a good general starting point for classifying things.”

Tyson humorously pointed out this debate is big only in the US, which he attributed to Disney’s creation of the lovable, dimwitted cartoon bloodhound named Pluto. School kids, grownups, op-ed writers all say Pluto is their favorite planet. “I am certain that the word ‘plutocracy’ is traceable to what Disney has done, so it’s hard to extricate the sentiment we have for the planet from the dog.”

Sykes said the IAU didn’t expand our perspective on planets, but narrow it. “The planet count went down, and what was the justification of that? The proponents have never given a good explanation of what was motivating that perspective.”

Tyson said numbers aren’t important, but words and definitions are, and we definitely need new ones.

Both scientists gave good arguments for their cause, and since I’m decidedly on the fence with this issue, I found myself leaning towards one option or the other, as each one spoke. Sykes, who wants to see Pluto reinstated as a planet, wants to take what we have and make it better, while Tyson, who thinks Pluto is a comet, wants to start over with new and better words and definitions.

It was an entertaining and educational debate with two well-spoken and intelligent scientists who sometimes weren’t very polite, however. (Sykes said, “When were’ not fighting we get along fine.”) The most important thing, they both agreed though, was that scientists are actually talking about this issue in the public eye and people are interested. But more importantly, the public is seeing the scientific process in action. They said this debate shouldn’t be about making things easy, or worrying about “not confusing the public.” Learning science shouldn’t be rote memorization of lists of objects, but a discussion of how objects are similar and different. “My recommendation to school teachers,” said Tyson “is to get the notion of counting things out of your system and comb the solar system for the richness of objects. Ask about different ways to combine the different objects in our solar system and have a discussion about their different properties.”

The debate will be available online, and we’ll post a link to it here when it is.

Sykes ended with his closing argument: “We both have issues with what happened with the IAU, its part of an ongoing presentation, but the important things is that the public gets to see the debate, and it’s not a battle over what list and what numbers you have, but the debate of the issues. That’s more important whether either of us have convinced you of one perspective. Science in this country is too much memorizing lists promulgated by those in authority. This is helping to expose the messy side of science. This debate is good and positive.”

Tyson ended by saying how charmed he is at the level of public interest in this subject. “How many sciences get to have their issues debated in the op-ed pages and comics?” He said he was happy with the word “planet” until all the data started pouring in from our explorations. “There should be a way to celebrate a new way to think about things. There ought to be a way to capture that” he said.

Obviously, this is not the last word on the subject from either scientist, or either side of the debate.

But that’s a good thing.

For more info on the Great Planet Debate.

August 14, 2008December 24, 2015 by Nancy Atkinson

Research and Technology to Help Psychological Issues of Space Travel

Long, lonely trips to Mars could pose psychological challenges for astronauts.

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Psychologists meeting this week at the American Psychological Association’s 116th Annual Convention are taking the time to discuss the challenges astronauts will face on the longer missions planned for NASA’s return to the moon and missions to Mars. Presenters at the first every symposium to address the psychological aspects of long-term spaceflight outlined the mental health challenges and introduced a new interactive computer program that will help address psychosocial issues in space. Psychologists said longer missions mean astronauts will be faced with immense psychological pressures as they adjust to being so far away from Earth, which could lead to depression and interpersonal conflicts. “Lessons learned from the past, research in extreme environments, training, conditioning, and countermeasures for psychological stress are some of the things NASA is in the process of addressing for the upcoming age of exploration,” said psychologist Marc Shepanek, PhD, from the Office of the Chief Health and Medical Officer at NASA.

Previously, not much thought had been given to the mental health of astronauts. These strong, intelligent and gifted astronauts seemed almost above psychological concerns. But these types of issues were brought to the forefront of everyone’s attention when astronaut Lisa Nowak was charged with attempted murder in a bizarre love triangle involving another astronaut. Historically, astronauts have been reluctant to admit to mental or behavioral health problems for fear of being grounded.

Psychologist James Carter, PhD, and his colleagues are in the process of developing a suite of interactive computer programs, dubbed the Virtual Space Station, using input from 13 veteran long-duration NASA astronauts who have flown on the International Space Station, Mir and Skylab. The system is being evaluated in a set of randomized controlled clinical trials. This interactive program will help astronauts prevent, detect, assess and manage their own psychosocial problems. They will learn how to cope with depression and how to resolve conflicts with other astronauts.

“Behavioral health problems can interfere with the success of the mission, especially on long-duration space flights like missions to the International Space Station, the moon and Mars. These self-guided software tools will provide private and immediate access to treatments even though the patient may be many miles from Earth,” Carter said in prepared remarks. The Virtual Space Station has already been deployed in Antarctica.

However, as astronauts aim to explore a new planet, the one they leave behind could be foremost on their minds. They will have limited contact with their families and radio communications with Mission Control will be delayed, possibly for as long as 40 minutes. In her presentation, family sociologist Phyllis Johnson, PhD, analyzed interviews with astronauts who had spent an extended amount of time in space. The astronauts identified what they felt was the role of NASA, themselves and their families in creating a “home away from home” during their flights. “For example, they emphasized the importance of regular communication regarding work, publicity and education, all of which provide connection to Earth and helped to reduce the perception of isolation,” said Johnson.

Psychologists also looked to history for guidance in future space missions. “The closest analogue to Mars exploration is the exploration of Earth,” said psychologist Peter Suedfeld, PhD. “Both maritime and terrestrial explorers struck off into the unknown, often for many years at a time.” Like space explorers, they had little or no communication with home, and had to devise ways of coping with unforeseen and unfamiliar hardships and dangers. Psychologists are re-examining sea and land voyagers’ diaries, logs and letters for a glimpse into how these explorers dealt with boredom, rebelliousness and dissent. They said it may be best way to predict some aspects of future long-duration missions.

News Source: EurekAlert

August 14, 2008December 24, 2015 by Nancy Atkinson

Mars Dust Grains Imaged by Atomic Force Microscope

3-D image of a dust grain from Phoenix's Atomic Force Microscope. Credit: NASA/JPL/Caltech/U of Arizona/U of Neuchatel

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What is Mars ubiquitous dust really like, close-up? Scientists from the Phoenix missions are finding out with the Atomic Force Microscope (AFM), an instrument that is providing the highest magnification of anything seen from another world. A couple of months ago the Phoenix Mars Lander used its optical microscope to image small grains of the Martian soil. Now, the spacecraft has switched on the AFM to take the first-ever 3-dimensional image of a single particle of Mars’ dust. The AFM can detail the shapes of particles as small as about 100 nanometers, about one one-thousandth the width of a human hair. That is about 100 times greater magnification the optical microscope. The article is rounded, and about one micrometer, or one millionth of a meter, across. It is a speck of the dust that cloaks Mars. Such dust particlets color the Martian sky pink, feed storms that regularly envelop the planet and produce Mars’ distinctive red soil.

“This is the first picture of a clay-sized particle on Mars, and the size agrees with predictions from the colors seen in sunsets on the Red Planet,” said Phoenix co-investigator Urs Staufer of the University of Neuchatel, Switzerland, who leads a Swiss consortium that made the microscope.

“Taking this image required the highest resolution microscope operated off Earth and a specially designed substrate to hold the Martian dust,” said Tom Pike, Phoenix science team member from Imperial College London. “We always knew it was going to be technically very challenging to image particles this small.”

The device took about a dozen years to develop. The AFM maps the shape of particles in three dimensions by scanning them with a sharp tip at the end of a spring. During the scan, invisibly fine particles are held by a series of pits etched into a substrate microfabricated from a silicon wafer.

“I’m delighted that this microscope is producing images that will help us understand Mars at the highest detail ever,” Staufer said. “This is proof of the microscope’s potential. We are now ready to start doing scientific experiments that will add a new dimension to measurements being made by other Phoenix lander instruments.”

“After this first success, we’re now working on building up a portrait gallery of the dust on Mars,” Pike added.

Mars’ ultra-fine dust is the medium that actively links gases in the Martian atmosphere to processes in Martian soil, so it is critically important to understanding Mars’ environment, the researchers said.

Phoenix's robotic arm scoop brought a sample of soil to MECA, which includes the AFM. Image: NASA/JPL/Caltech/U of Arizona

The particle seen in the atomic force microscope image was part of a sample scooped by the robotic arm from the “Snow White” trench and delivered to Phoenix’s microscope station in early July. The microscope station includes the optical microscope, the atomic force microscope and the sample delivery wheel. It is part of a suite of tools called Phoenix’s Microscopy, Electrochemistry and Conductivity Analyzer.

Source: Phoenix News Site

August 14, 2008December 24, 2015 by Nancy Atkinson

Former Astronaut to Bike Across US for Education

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Former NASA astronaut and Rocketplane test pilot John Herrington has a new state-of-the-art vehicle of choice: a bike. But itâ€™s a touring bike fully loaded with a GPS, laptop, broadband phone, and digital and video cameras. Herrington is embarking on a cross country bike trek to promote and encourage student participation in science, technology, engineering and mathematics (STEM). Herrington, once a college dropout who went on to fly in space in 2002 on the STS-113 mission, hopes he can help make a difference and impact on children by sharing his experiences and providing web-based, hands-on activities using STEM skills to solve problems while following his journey. Herrington also wants to encourage children to pursue their dreams and seek out exciting opportunities. “The generation that grew up in the age of the Apollo program and the journey to the moon was motivated by the excitement of space and the possibilities that it brought to the nation,” said Herrington. “Those kinds of possibilities to explore the unknown and make new discoveries still exist, but we must motivate students to learn and have a way to connect what they learn to what they do on a daily basis.”

Herrington began his coast-to-coast tour yesterday (August 13) from Cape Flattery in Washington state and will finish at Cape Canaveral in Florida. The trip is expected to take three months, and Herrington will stop at schools along the way to talk about his “journey to the space program, the wonders of flying in space and the need for students to realize their potential that lies within,” he said.

Herrinton by the Pacific Ocean at the start of his "Rocketrek" tour

Students can log into Herrington’s blog for daily updates and new problem solving challenges. Herrington, the first Native American in space will be especially focusing on Native students, hoping to kindle imagination and motivation. “I was once an unmotivated student, looking for something that sparked my fire,” he said. “I found it as a rock-climber on a survey crew, learning the application of mathematics from the side of a cliff. That experience inspired me to return to school and ultimately led to my career as an astronaut.”

As part of the crew of the space shuttle Endeavour in November of 2002, Herrington conducted three spacewalks to help in construction of the International Space Station, logging just under 20 hours of EVAs. He left NASA in 2005 to join Rocketplane Global as a test pilot. He left Rocketplane in December 2007 to pursue other opportunities, which obviously, includes biking.

“Sometimes it takes someone outside of our normal circle of friends and family to shine a light in our direction and help us along,” Herrington continued. “As I set out on this bike ride and try to make the learning practical and fun, I hope to also show students that it takes commitment and effort, both mental and physical, to accomplish your goals.”

Herrington getting his bike ready for takeoff. Credit: Rocketrek

Here are the topics Herrington will be focusing on in his educational endeavors:

Science:
Caloric intake and heart rate in relation to overall health
Hydration, dehydration, hypothermia
Weather, wind velocity, ground and air speed, relative motion
Technology:
Bike composition and weight/ comparison to space shuttle/station
Bike maintenance and repair
Getting power to electronics (i.e. batteries, solar)
Global Positioning System (GPS)
Digital camera technology
Engineering:
Velocity and torque
Mass and weight
Friction and measurements
Math:
Basic math
Addition and subtraction
Geometry, trigonometry and physics

News Source: John Herrington’s RocketTrek site

August 13, 2008December 24, 2015 by Nancy Atkinson

Solving the Asteroid â€“ Meteorite Puzzle

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Astronomers studying ways to deal with incoming near-Earth asteroids (NEA) that might be on a collision course with our planet want to know in detail what these space rocks are made of. The better they “know the enemy” the better they can come up with ways to destroy or change the course of NEAs. Since we’ve only studied a couple of asteroids up close with spacecraft, the best way to learn more about the composition of asteroids should be fairly easy: just look at meteorites that fall to Earth, which are small chunks of asteroids. But in doing so, researchers discovered quite a huge discrepancy. The vast majority of asteroids that whiz by Earth are of a type that matches only a tiny fraction of the meteorites that most frequently hit our planet. This difference has had astronomer scratching their heads. But a team of researchers has now found what it believes is the answer to the puzzle. The smaller rocks that most often fall to Earth, it seems, come straight in from the main asteroid belt out between Mars and Jupiter, rather than from the near-Earth asteroid population.

The researchers studied the spectral signatures of near-Earth asteroids and compared them with spectra obtained on Earth from the thousands of meteorites found on Earth. But the more they looked, the more they found that most NEAs — about two-thirds of them — match a specific type of meteorites called LL chondrites, which only represent about 8 percent of meteorites.

“Why do we see a difference between the objects hitting the ground and the big objects whizzing by?” asked Richard Binzel, a professor from MIT. “It’s been a headscratcher.” As the effect became gradually more and more noticeable as more asteroids were analyzed, “we finally had a big enough data set that the statistics demanded an answer. It could no longer be just a coincidence.”

Way out in the main belt, the population is much more varied, and approximates the mix of types that is found among meteorites. But why would the things that most frequently hit us match this distant population better than it matches the stuff that’s right in our neighborhood?

An obscure effect that was discovered long ago was recently recognized as a significant factor in moving asteroids around and putting them on a fast track towards the inner solar system, called the Yarkovsky effect.

This effect causes asteroids to change their orbits as a result of the way they absorb the sun’s heat on one side and radiate it back later as they rotate around, which alters the object’s path. This effect acts much more strongly on the smallest objects, and only weakly on the larger ones.

So, for smaller sized space rocks– the kinds of things that end up as typical meteorites — the Yarkovsky effect plays a major role, moving them with ease from throughout the asteroid belt on to paths that can head toward Earth. For larger asteroids a kilometer or so across, the kind that we worry about as potential threats to the Earth, the effect is so weak it can only move them small amounts.

The new study is also good news for protecting the planet. One of the biggest problems in figuring out how to deal with an approaching asteroid, if and when one is discovered on a potential collision course, is that they are so varied. The best way of dealing with one kind might not work on another.

But now that this analysis has shown that the majority of near-Earth asteroids are of this specific type — stony objects, rich in the mineral olivine and poor in iron — it’s possible to concentrate most planning on dealing with that kind of object, Binzel says. “Odds are, an object we might have to deal with would be like an LL chondrite, and thanks to our samples in the laboratory, we can measure its properties in detail,” he says. “It’s the first step toward ‘know thy enemy’.”

News Source: MIT

August 13, 2008December 24, 2015 by Nancy Atkinson

Have a Question About Space? Ask an Astronaut

Astronaut Greg Chamitoff on board the ISS. Credit: NASA

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Astronauts are usually gregarious and quite pleasant people who like to share their experiences of living and working in space. Current International Space Station resident Greg Chamitoff is no different, and he is now ready and waiting to answer any burning questions you may have about human space flight. NASA offers a “Ask the Expert” website for many of its human missions, where the public can submit questions and astronauts or other NASA personnel answer with written and/or audio replies. But the past few space shuttle missions have been so jam-packed with ISS construction activities, there hasn’t been time in the schedule for astronauts to answer any questions from the public. However, Chamitoff will be on board the ISS for a couple of months, and he has some time to answer a few questions. Questions will be transmitted to Greg from Mission Control each week and his answers to a few of them will be available here.

Don’t know what to ask? NASA has a few guidelines:

Try to avoid asking a question that has been answered often on previous missions.

Normally the questions most often answered are those more specific to the current crew and mission.

Do your homework and review information about the station and current activities when you compose your question.

Check out the archives of past questions answered here. There you can even listen to audio of questions answered by the STS-107 crew of Columbia. They really were a great crew.

NASA also has a few rules about asking questions:

Stay on topic.

No profanity, sexually explicit or discriminatory material.

Basically, be nice. So, ask away!

News Source: NASA

August 13, 2008December 24, 2015 by Nancy Atkinson

This Week’s “Where In The Universe” Challenge

It’s time once again for this week’s Where In The Universe challenge. Take a look at the image above and try to determine where in the universe this image was taken. Give yourself extra points if you can name the spacecraft responsible for taking this image. As always, no peeking below for the before you make your guess.

Here’s one more image of this object.

Ready for the answer?

These are images of Neptune’s moon Proteus. Needless to say, Proteus is not one of the better-known moons of our solar system. Did you recognize it? Proteus was discovered in 1989 by the only spacecraft that has flown by Neptune, Voyager 2. Though Proteus (400 km diameter) is larger than Neptune’s better known moon, Nereid (340 km, which was discovered in 1949 by Gerard Kuiper) Proteus was not discovered earlier because it is very dark and so close to Neptune that it is difficult to see in the glare of the much brighter planet.

Proteus has an irregular almost box-like shape, and scientists believe it is probably about as big as an irregular body can be before its gravity pulls it into a more spherical configuration.

There’s not a lot of action on Proteus. The heavily cratered surface shows no signs of geologic activity.

Other than those facts, there’s not much to say about Proteus. As Bill Arnett says on his Nine Planets website, “We know next to nothing about Proteus.” We’ve not sent a spacecraft to go visit and study Neptune and its moons specifically, and although NASA was considering sending a probe to Neptune a few years ago, it appears such a mission has been put on the back burner.

How’d you do in this week’s challenge?