Posted on by Fraser Cain

Methane Release Raised Earth Temperatures 180 Million Years Ago

Western Hemisphere. Image credit: NASA Click to enlarge
Open University researchers have uncovered startling new evidence about an extreme period of a sudden, fatal dose of global warming some 180 million years ago during the time of the dinosaurs. The scientists’ findings could provide vital clues about climate change happening today and in the future.

The OU Department of Earth Sciences team, PhD student Dave Kemp and supervisors Drs. Angela Coe and Anthony Cohen, along with Dr. Lorenz Schwark of the University of Cologne, discovered evidence suggesting that vast amounts of methane gas were released to the atmosphere in three massive ‘methane burps’ or pulses. The addition of methane, a greenhouse gas, to the atmosphere had a severe impact on the environment, warming Earth about 10 C, and resulting in the extinction of a large number of species on land and in the oceans.

Dr Angela Coe says: “We’ve known about this event for a few years through earlier work by our team and others, but there’s been a great deal of uncertainty about its precise size, duration, and underlying cause. What our present study shows is that this methane release was not just one event, but 3 consecutive pulses. Importantly, our data demonstrate that each individual pulse was very rapid. Also, whilst the methane release was very quick, we’ve found that the recovery took much longer, occurring over a few hundred thousand years”.

The methane came from gas hydrate, a frozen mixture of water and methane found in huge quantities on the seabed. This hydrate suddenly melted, allowing the methane to escape. The OU researchers based their findings on geochemical analyses of mudrocks that are preserved along the Yorkshire coast near Whitby, UK, and date from the Jurassic Period of geological time.

Dave Kemp, whose PhD is funded by the Natural Environment Research Council (NERC), says: “The methane was released because slight wobbles in the Earth’s orbit periodically bring our planet closer to the Sun, warming the oceans sufficiently to melt the vast reserves of hydrate. We believe that this effect was compounded by warming from greenhouse gases from volcanoes. After the methane was released into the atmosphere from the seabed it reacted rapidly with oxygen to form carbon dioxide. Carbon dioxide is also a powerful greenhouse gas that persists in the atmosphere for many hundreds of years, and it was this gas which caused such a massive global warming effect”.

Dr Anthony Cohen adds: “One of the most important aspects of the study is that it provides an accurate timescale for how the Earth, and life, reacted to a sudden increase in atmospheric carbon dioxide. Today we are releasing large amounts of carbon dioxide to the atmosphere, primarily through the burning of fossil fuels. It is possible that the rate at which carbon dioxide is being added to the atmosphere now actually outstrips the rate at which it was added 180 million years ago. Given that the effects were so devastating then, it is extremely important to understand the details of past events in order to better comprehend present-day climate change. With this information, we are better informed about what action needs to be taken to mitigate or avoid some of the potential detrimental future effects”.

NASA Astrobiology

Posted on by Fraser Cain

Ghostly Spokes in the Rings

An image showing faint, narrow spokes in the outer B ring. Image credit: NASA/JPL/SSI Click to enlarge
Scientists are celebrating the first Cassini spacecraft sighting of spokes, the ghostly radial markings discovered in Saturn’s rings by NASA’s Voyager spacecraft 25 years ago.

A sequence of images taken on the side of the rings not illuminated by the sun has captured a few faint, narrow spokes in the outer B ring, about 3,500 kilometers long and about 100 kilometers wide (2,200 miles by 60 miles).

The images can be seen at: http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and http://ciclops.org .

Previously, scientists believed the visibility of spokes depended on the elevation of the sun above the rings. The less sunlight, the more visible the spokes. For this reason, they weren’t expecting to see spokes until later in the mission when the sun angle will be low.

In Voyager images from 25 years ago, the spokes appeared dark when seen at low sun angles and bright when seen at high sun angles. This behavior indicated that they were comprised of extremely small icy particles. Since Voyager days, spokes had been seen in images taken by NASA’s Hubble Space Telescope. The new Cassini images were taken at very high sun angles, where small particles can brighten substantially, making them more visible.

Determining the timing in the appearance of spokes will be of intense interest and will require monitoring spoke activity from a variety of geometries over several years. “Cassini has found that the Saturn Kilometric Radiation period has changed since Voyager, which though hard to believe, may mean that the rotation of Saturn’s interior has changed,” said Dr. Carolyn Porco, Cassini imaging team leader at the Space Science Institute in Boulder, Colo., and one of the first individuals to study spokes in Voyager images. “That would be a finding of enormous consequence, so we’ll be looking very closely to see if the frequency of spoke activity has changed too.”

Porco’s analysis of spokes in the early 1980s found that these narrow arrangements of small particles came and went with a period equal to that of the powerful bursts of radio waves, called Saturn Kilometric Radiation, discovered by Voyager and coming from Saturn’s magnetic field. This association indicated that spokes were a phenomenon involving electromagnetic effects due to Saturn’s magnetic field.

There is no commonly accepted theory for the creation of spokes. Some ideas suggest that spokes result from meteoroid impacts onto the rings; others suggest that they are created by instability in Saturn’s magnetic field, which surrounds the planet, near the rings. Whatever the cause, imaging team members will study the new spoke images and maintain their vigil for additional spoke sightings.

Cassini also completed a flyby of Saturn’s moon Titan on Wednesday, Sept. 7. During that flyby, one of two solid-state recorders on board the spacecraft failed to record science data as planned. The spacecraft team is troubleshooting the cause of the anomaly, and early indications point to a software problem that would be correctable with no long-term impacts. About half of the planned science data was received.

This was Cassini’s eighth flyby out of 45 Titan flybys planned in the nominal four-year tour.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Shoreline Found on Titan

The boundary of the bright (rough) region and the dark (smooth) region appears to be a shoreline. Image credit: NASA/JPL/SSI Click to enlarge
Images returned during Cassini’s recent flyby of Titan show captivating evidence of what appears to be a large shoreline cutting across the smoggy moon’s southern hemisphere. Hints that this area was once wet, or currently has liquid present, are evident.

“We’ve been looking for evidence of oceans or seas on Titan for some time. This radar data is among the most telling evidence so far for a shoreline,” said Steve Wall, radar deputy team leader from NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

The new radar images can be seen at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

The images show what looks like a shoreline dividing a distinct bright and dark region roughly 1,700 kilometers long by 170 kilometers wide (1,060 by 106 miles). Directly to the right of a bright and possibly rough area is one that is very dark and smooth.

“This is the area where liquid or a wet surface has most likely been present, now or in the recent past, said Wall. “Titan probably has episodic periods of rainfall or massive seepages of liquid from the ground.”

The brightness patterns in the dark area indicate that it may once have been flooded with liquid that may now have partially receded. Bay-like features also lead scientists to speculate that the bright-dark boundary is most likely a shoreline.

“We also see a network of channels that run across the bright terrain, indicating that fluids, probably liquid hydrocarbons, have flowed across this region,” said Dr. Ellen Stofan, Cassini associate radar team member from Proxemy Research, Laytonsville, Md.

Taken together with the two other radar passes in October 2004 and February 2005, these very high resolution images have identified at least two distinct types of drainage and channel formation on Titan. Some channels in images from this pass are long and deep, with angular patterns and few tributaries, suggesting that fluids flow over great distances. By contrast, others show channels that form a denser network that might indicate rainfall.

Dr. Larry Soderblom with the U.S. Geological Survey in Flagstaff, Ariz., said, “It looks as though fluid flowed in these channels, cutting deeply into the icy crust of Titan. Some of the channels extend over 100 kilometers (60 miles). Some of them may have been fed by springs, while others are more complicated networks that were likely filled by rainfall.”

Titan has an environment somewhat similar to that of Earth before biological activity forever altered the composition of Earth’s atmosphere. The major difference on Titan, however, is the absence of liquid water, and Titan’s very low temperature. With a thick, nitrogen-rich atmosphere, Titan was until recently presumed to hold large seas or oceans of liquid methane. Cassini has been in orbit around Saturn for a year and has found no evidence for these large seas.

Cassini encountered an anomaly with one of two solid-state recorders during the Sept. 7 close flyby, resulting in some data not being recorded. Half of the data from the flyby was received, much to the delight of anxious scientists. The spacecraft team is troubleshooting the cause, and early indications point to a software problem that would be correctable with no long-term impacts.

This was Cassini’s eighth out of 45 Titan flybys planned in the nominal four-year tour. The next radar pass will be Oct. 26 when the team will focus on the Huygens probe landing site close to the equator.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA?s Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument team is based at JPL, working with team members from the United States and several European countries.

Original Source: NASA/JPL/SSI News Release

Posted on by Mark Mortimer

Book Review: The Rocket Company

The particular dream of this book is where people end up easily, routinely and safely flying into space from Earth. In real life, many people and corporations address this topic seemingly at regular intervals. NASA has its own unique capability to start projects along this road only to shy away just before culmination. Jules Verne had his plans, purely fictional ideas for travelling to the moon. Wernher Von Braun had his own plans and dreams. Most daydreamers look at only certain aspects. Engineers, of course, focus on resolving technical issues. Economists might envision profits greater than any known on Earth. Philosophers vouchsafe interstellar travel as the ultimate test for humankind, and dream to pass the test. Within the mind, such events and circumstances can easily shape into a solid looking mirage. Often, that is exactly where they stay, as reality tends to be a lot different and usually much more challenging.

In The Rocket Company, Stiennon and Hoerr put paper to their daydreaming engineering ways. Their premise for getting people safely and effectively space faring begins with an investors group with pocket books just large enough to bank role everyone’s needs. Next, the investors go hire the best engineers with well above typical salary levels and then give them all the babysitting they need to build their rocket ship. Rather than just listing the systems, sub-systems and components, the authors do an excellent job of introducing production elements at appropriate times. First the flight trajectory defines the requirements. Market cases frame the payload size. Then many of the main elements of the craft get analysed and defined. The analysis does include a lot of engineer speak which is great for said specialists but not so much for others.

However, don’t let the preceding fool you into thinking this book is a dry rendition of systems engineering case studies. It is not. The authors artfully and smoothly wrap all the engineer speak into a fictional package that makes reading it a pleasure. The frame of reference for the reader is of looking over the shoulder of the company’s chief documenter. From this first person perspective, the reader is treated to people discussing the pro’s and con’s of various fuel mixtures, we listen to shouting in the boardroom while options are discussed and we taste the thrill of watching the test vehicle successfully launch.

By using this fictional surround to convey their impression of requirements and resolutions, the authors ensure that somewhat dry subject matter gets a fresh and interesting face. They introduce problems like slowing a feedback response to be compatible with human characteristics. Then, they present discussions amongst the fictional characters on some juicy historical similarities. Last, they sum up the issue by having the company’s expert engineer give the appropriate answer for this difficulty. And this is the beauty of fiction and daydreaming as the results work first time.

By using a person in a fictional company to present technical parameters studies, the authors successfully walk a very challenging tight rope. On one side is the chasm of detail. If they fell there, the book would likely have reams of tables of weight, cost and capability. This way they’d have a true technical reference but a very dry and dated one. On the other side of the rope, the chasm leads to pure fiction. That is, the authors provide a good story but what value is it in actually getting people into space? Skilfully though, the authors place the readers between these two gaping pitfalls and nicely balance the rocket design and business case with the fictional encounters of people living the lives within a fictitious company.

In consideration, there must be something people are just missing. We’ve put humans on the moon, we’ve dug tunnels joining Britain to France, and we’ve raised buildings towering high into the sky. So why are we still moribund on this planet? Many answers jump forth, but let the book The Rocket Company by Patrick Stiennon and David Hoerr show you one avenue to escape this tribulation. Sometimes dreams can turn into reality. This is one which many people would happily wish to come true.

Review by Mark Mortimer

Read more reviews online, or purchase a copy from Amazon.com.

Posted on by Fraser Cain

What’s Up This Week – September 19 – September 25, 2005

Cassini image of Saturn. Image credit: NASA/JPL. Click to enlarge.
Monday, September 19 – On this day in 1848, William Boyd was watching Saturn – and discovered its moon – Hyperion. If you’re up early this morning, why not take a look at the “Ring King”? It’s making a very spectacular pass through the constellation of Cancer right now and is wonderfully close to the M44! If you’re looking telescopically, be sure to power up for the Cassini Division and even small telescopes can spot its many moons.

Also today in 1988, Israel launched its first satellite. How long has it been since you’ve watched an ISS pass or an iridium flare? Both are terrific events that don’t require any special equipment to be seen. Be sure to check with Heaven’s Above for accurate times and passes in your location and enjoy!

Since we will only have a short time until the Moon rises tonight, let’s follow the progress of a variable star over the next week. Eta Aquilae is one of the most fascinating stars in the sky to watch and it doesn’t even require a telescope. Just look less than one fist-width due south of Altair…

Discovered by Pigot in 1784, this cepheid class variable has a precision change rate of over a magnitude in a period of 7.17644 days. During this time it will reach of maximum of magnitude 3.7 and decline slowly over 5 days to a minimum of 4.5… Yet it only takes two days to brighten again! This period of expansion and contraction makes Eta very unique. To help gauge these changes, compare Eta to Beta on Altair’s same southeast side. When Eta is at maximum, it will be about equal in brightness.

Tuesday, September 20 – On this night in 1948, the 48″ Schmidt telescope at Mt. Palomoar was busy taking pictures. The first photographic plate was being exposed on a galaxy by the same man who ground and polished the corrector plate for this scope – Hendricks. His object of choice was reproduced as panel 18 in the Hubble Atlas of Galaxies and tonight we’ll join his vision as we take a look at the fantastic M31 – Andromeda Galaxy.

Seasoned amateur astronomers can literally point to the sky and show you the location of the M31, but perhaps you have never tried. Believe it or not, this is an easy galaxy to see unaided from even a modest dark sky site. Simply look to the east well after twilight and identify the large diamond-shaped pattern of stars that stretches around a handspan. This is the “Great Square of Pegasus”. The northernmost star is Alpha, and it is here we will begin our hop. Stay with the north chain of stars and look four finger-widths away for an easily seen star. The next along the chain is about three finger-widths away… And we’re almost there. Two more finger-widths to the north and you will see a dimmer star that looks like it has something smudgy nearby. That’s no cloud… That’s the Andromeda Galaxy. Congratulations. You didn’t even need a telescope.

Now get out those optics and enjoy one of the finest, largest and brightest in the sky!

Wednesday, September 21 – With plenty of time to spare before the Moon rises tonight, let’s head on to Capricornus and drop about four finger-widths south of its northeastern most star – Delta – and have a look at M30.

Discovered in 1764 by Charles Messier, binocular observers will spot this small, but attractive, globular cluster easily in the same field with star 41. For telescopic observers, you will find a dense core region and many chains of resolvable stars in this 40,000 light year distant object. Power up.

Tonight, watch as the Moon rises about two hours after sunset. Around a half hour later, you will see Mars join the show as well.

Thursday, September 22 – Today is the Autumnal Equinox, and will occur at 6:23 p.m. EDT. This marks the first day of the Fall season for the Northern Hemisphere and we astronomers welcome back earlier dark skies!

On this universal date for viewers in Hawaii, and most portions of Australia and New Zealand, the Moon will occult one of the Plieades’ stars – Alcyone. What a great event! Be sure to check this IOTA webpages for times in your area.

Now let’s get some more practice in Capricornus, as tonight we’ll take on a more challenging target with confidence. Locate the centermost bright star in the northern half of the constellation – Theta – because we’re headed for the “Saturn Nebula”.

Three finger-widths north of Theta you will see dimmer Nu, and only one finger-width west is NGC 7009. Nicknamed the “Saturn Nebula”, this wonderful blue planetary is around 8th magnitude and achievable in small scopes and large binoculars. Even at moderate magnification, you will see the elliptical shape which gave rise to its moniker. With larger scopes, those “ring like” projections become even clearer, making this challenging object well worth the hunt. You can do it!

Friday, September 23 – Check out the western skyline tonight about a half hour after sunset. The bright planet – Jupiter – is now almost lost, but in 1846 on this day, Johann Galle of the Berlin Observatory found another. This was the first time that Neptune was seen and identified visually.

Thanks to tonight’s much darker skies, you too, will have the same opportunity. Start by identifying Theta once again. Two finger-widths away to the northeast is dim star 29. Now, using your binoculars or finderscope, between them you will see another star and this is our marker. When you have located that star, Neptune is just to its northeast and will be the brightest object in the field with the exception of our marker star. It’s just that easy!

On this day in 1962, the prime time cartoon “The Jetsons” first premiered. Think of all the technology this inspired as tonight we kick back to watch the Alpha Aurigid meteor shower. Relax, face northeast and look for the radiant near Capella. The fall rate is around 12 per hour, and they are fast and leave trails!

Saturday, September 24 – In 1970, the first unmanned, automated return of lunar material to the Earth occurred on this day when the Soviet’s Luna 16 returned with three ounces of the Moon. If we think back, the lowest passing of that Moon to the south occured not long ago. By tomorrow morning it will have reached its highest point just before the Sun rises and will be nearly overhead.

For viewers in Northern Europe, the Moon will occult bright star 136 Taurii on this universal date. Be sure to check this IOTA webpages for a listing of times and locations in your area.

For the rest of us, we’ve got around four hours to play before the Moon brightens the skies. So, are we ready to try for the “Helix”?

Located in a sparsely populated area of the sky, this intriguing target is about a fist width due northwest of bright Formalhaut and about a fingerwidth west of Upsilon Aquarii. While the NGC 7293 is also a planetary nebula, its entirely different than most… It’s a very large and more faded edition of the M57! On a clear, dark night it can be spotted with binoculars since it spans almost one quarter a degree of sky. Using a telescope, stay at lowest power and widest field, because it is so large. It you have an OIII filter, this faded “ring” becomes a braided treat!

Sunday, September 25 – Now, are you ready for something really exciting? There’s a new comet in town and its name is 2005/P3 SWAN. At close to magnitude 10, this is not a comet you are going to see in binoculars or a small telescope, but for those with larger instruments and a northern position, you are going to like this!

Now, mind you… Ursa Major is now a morning constellation for most of us, but 2005/P3 SWAN will be mixing it up with both the Owl Nebula and the M108! The predicted path charts put it about 1 degree southeast of the M97. Happy Hunting!

The skies are getting darker and the times are getting earlier. Let the galaxy hunt begin! Until next week, may all your journeys be at light speed…. ~Tammy Plotner

Posted on by Fraser Cain

New Details About Return to the Moon

Astronauts could return to the Moon as early as 2018. Image credit: NASA/JPL. Click to enlarge.
Before the end of the next decade, NASA astronauts will again explore the surface of the moon. And this time, we’re going to stay, building outposts and paving the way for eventual journeys to Mars and beyond. There are echoes of the iconic images of the past, but it won’t be your grandfather’s moon shot.

This journey begins soon, with development of a new spaceship. Building on the best of Apollo and shuttle technology, NASA’s creating a 21st century exploration system that will be affordable, reliable, versatile, and safe.

The centerpiece of this system is a new spacecraft designed to carry four astronauts to and from the moon, support up to six crewmembers on future missions to Mars, and deliver crew and supplies to the International Space Station.

The new crew vehicle will be shaped like an Apollo capsule, but it will be three times larger, allowing four astronauts to travel to the moon at a time.

The new spacecraft has solar panels to provide power, and both the capsule and the lunar lander use liquid methane in their engines. Why methane? NASA is thinking ahead, planning for a day when future astronauts can convert Martian atmospheric resources into methane fuel.

The new ship can be reused up to 10 times. After the craft parachutes to dry land (with a splashdown as a backup option), NASA can easily recover it, replace the heat shield and launch it again.

Coupled with the new lunar lander, the system sends twice as many astronauts to the surface as Apollo, and they can stay longer, with the initial missions lasting four to seven days. And while Apollo was limited to landings along the moon’s equator, the new ship carries enough propellant to land anywhere on the moon’s surface.

Once a lunar outpost is established, crews could remain on the lunar surface for up to six months. The spacecraft can also operate without a crew in lunar orbit, eliminating the need for one astronaut to stay behind while others explore the surface.

Safe and reliable
The launch system that will get the crew off the ground builds on powerful, reliable shuttle propulsion elements. Astronauts will launch on a rocket made up of a single shuttle solid rocket booster, with a second stage powered by a shuttle main engine.

A second, heavy-lift system uses a pair of longer solid rocket boosters and five shuttle main engines to put up to 125 metric tons in orbit — about one and a half times the weight of a shuttle orbiter. This versatile system will be used to carry cargo and to put the components needed to go to the moon and Mars into orbit. The heavy-lift rocket can be modified to carry crew as well.

Best of all, these launch systems are 10 times safer than the shuttle because of an escape rocket on top of the capsule that can quickly blast the crew away if launch problems develop. There’s also little chance of damage from launch vehicle debris, since the capsule sits on top of the rocket.

The Flight Plan
In just five years, the new ship will begin to ferry crew and supplies to the International Space Station. Plans call for as many as six trips to the outpost a year. In the meantime, robotic missions will lay the groundwork for lunar exploration. In 2018, humans will return to the moon. Here’s how a mission would unfold:

A heavy-lift rocket blasts off, carrying a lunar lander and a “departure stage” needed to leave Earth’s orbit. The crew launches separately, then docks their capsule with the lander and departure stage and heads for the moon.

Three days later, the crew goes into lunar orbit. The four astronauts climb into the lander, leaving the capsule to wait for them in orbit. After landing and exploring the surface for seven days, the crew blasts off in a portion of the lander, docks with the capsule and travels back to Earth. After a de-orbit burn, the service module is jettisoned, exposing the heat shield for the first time in the mission. The parachutes deploy, the heat shield is dropped and the capsule sets down on dry land.

Into the Cosmos
With a minimum of two lunar missions per year, momentum will build quickly toward a permanent outpost. Crews will stay longer and learn to exploit the moon’s resources, while landers make one way trips to deliver cargo. Eventually, the new system could rotate crews to and from a lunar outpost every six months.

Planners are already looking at the lunar south pole as a candidate for an outpost because of concentrations of hydrogen thought to be in the form of water ice, and an abundance of sunlight to provide power.

These plans give NASA a huge head start in getting to Mars. We will already have the heavy-lift system needed to get there, as well as a versatile crew capsule and propulsion systems that can make use of Martian resources. A lunar outpost just three days away from Earth will give us needed practice of “living off the land” away from our home planet, before making the longer trek to Mars.

Original Source: NASA News Release

Posted on by Fraser Cain

Leftover Material Caused the Late Heavy Bombardment

Lunar surface. Image credit: LPI Click to enlarge
University of Arizona and Japanese scientists are convinced that evidence at last settles decades-long arguments about what objects bombarded the early inner solar system in a cataclysm 3.9 billion years ago.

Ancient main belt asteroids identical in size to present-day asteroids in the Mars-Jupiter belt — not comets — hammered the inner rocky planets in a unique catastrophe that lasted for a blink of geologic time, anywhere from 20 million to 150 million years, they report in the Sept. 16 issue of Science.

However, the objects that have been battering our inner solar system after the so-called Late Heavy Bombardment ended are a distinctly different population, UA Professor Emeritus Robert Strom and colleagues report in the article, “The Origin of Planetary Impactors in the Inner Solar System.”

After the Late Heavy Bombardment or Lunar Cataclysm period ended, mostly near-Earth asteroids (NEAs) have peppered the terrestrial region.

Strom has been studying the size and distribution of craters across solar system surfaces for the past 35 years. He has long suspected that two different projectile populations have been responsible for cratering inner solar system surfaces. But there’s been too little data to prove it.

Now asteroid surveys conducted by UA’s Spacewatch, the Sloan Digital Sky Survey, Japan’s Subaru telescope and the like have amassed fairly complete data on asteroids down to those with diameters of less than a kilometer. Suddenly it has become possible to compare the sizes of asteroids with the sizes of projectiles that blasted craters into surfaces from Mars inward to Mercury.

“When we derived the projectile sizes from the cratering record using scaling laws, the ancient and more recent projectile sizes matched the ancient and younger asteroid populations smack on,” Strom said. “It’s an astonishing fit.”

“One thing this says is that the present-day size-distribution of asteroids in the asteroid belt was established at least as far back as 4 billion years ago,” UA planetary scientist Renu Malhotra, a co-author of the Science paper, said. “Another thing it says is that the mechanism that caused the Late Heavy Bombardment was a gravitational event that swept objects out of the asteroid belt regardless of size.”

Malhotra discovered in previous research what this mechanism must have been. Near the end of their formation, Jupiter and the other outer gas giant planets swept up planetary debris farther out in the solar system, the Kuiper Belt region. In clearing up dust and pieces leftover from outer solar system planet formation, Jupiter, especially, lost orbital energy and moved inward, closer to the sun. That migration greatly enhanced Jupiter’s gravitational influence on the asteroid belt, flinging asteroids irrespective of size toward the inner solar system.

Evidence that main belt asteroids pummeled the early inner solar system confirms a previously published cosmochemical analysis by UA planetary scientist David A. Kring and colleagues.

“The size distribution of impact craters in the ancient highlands of the moon and Mars is a completely independent test of the inner solar system cataclysm and confirms our cosmochemical evidence of an asteroid source,” Kring, a co-author of the Science paper, said.

Kring was part of a team that earlier used an argon-argon dating technique in analyzing impact melt ages of lunar meteorites — rocks ejected at random from the moon’s surface and that landed on Earth after a million or so years in space. They found from the ages of the “clasts,” or melted rock fragments, in the breccia meteorites that all of the moon was bombarded 3.9 billion years ago, a true global lunar cataclysm. The Apollo lunar sample analysis said that asteroids account for at least 80 percent of lunar impacts.

Comets have played a relatively minor role in inner solar system impacts, Strom, Malhotra and Kring also conclude from their work. Contrary to popular belief, probably no more than 10 percent of Earth’s water has come from comets, Strom said.

After the Late Heavy Bombardment, terrestrial surfaces were so completely altered that no surface older than 3.9 billion years can be dated using the cratering record. Older rocks and minerals are found on the moon and Earth, but they are fragments of older surfaces that were broken up by impacts, the researchers said.

Strom said that if Earth had oceans between 4.4 billion and 4 billion years ago, as other geological evidence suggests, those oceans must have been vaporized by the asteroid impacts during the cataclysm.

Kring also has developed a hypothesis that suggests that the impact events during Late Heavy Bombardment generated vast subsurface hydrothermal systems that were critical to the early development of life. He estimated that the inner solar system cataclysm produced more than 20,000 craters between 10 kilometers to 1,000 kilometers in diameter on Earth.

Inner solar system cratering dynamics changed dramatically after the Late Heavy Bombardment. From then on, the impact cratering record reflects that most objects hitting inner solar system surfaces have been near-Earth asteroids, smaller asteroids from the main belt that are nudged into terrestrial-crossing orbits by a size-selective phenomenon called the Yarkovsky Effect.

The effect has to do with the way asteroids unevenly absorb and re-radiate the sun’s energy. Over tens of millions of years, the effect is large enough to push asteroids smaller than 20 kilometers across into the jovian resonances, or gaps, that deliver them to terrestrial-crossing orbits. The smaller the asteroid, the more it is influenced by the Yarkovsky Effect.

Planetary geologists have tried counting craters and their size distribution to get absolute ages for surfaces on the planets and moons.

“But until we knew the origin of the projectiles, there has been so much uncertainty that I thought it could lead to enormous error,” Strom said. “And now I know I’m right. For example, people have based the geologic history of Mars on the heavy bombardment cratering record, and it’s wrong because they’re using only one cratering curve, not two.”

Attempts to date outer solar system bodies using the inner solar system cratering record is completely wrong, Strom said. But it should be possible to more accurately date inner solar system surfaces once researchers determine the cratering rate from the near-Earth asteroid bombardment, he added.

The authors of the Science paper are Strom, Malhotra and Kring from the University of Arizona Lunar and Planetary Laboratory, and Takashi Ito and Fumi Yoshida of National Astronomical Observatory, Tokyo, Japan.

Original Source: UA News Release

Posted on by Fraser Cain

What the Ground Telescopes Saw During Deep Impact

Mid-infrared image of comet 9P/Tempel 1 after the Deep Impact collision. Image credit: NAOJ Click to enlarge
When NASA’s Deep Impact mission ploughed into comet 9P/Tempel 1 on July 4th of this year, the giant telescopes on Mauna Kea had a unique view of the massive cloud of dust, gas and ice expelled during the collision.

A series of coordinated observations, made under ideal conditions by the world’s largest collection of big telescopes, delivered surprising new insights into the ancestry and l7ife cycles of comets. Specifically, materials beneath the comet’s dusty skin reveal striking similarities between two families of comets where no relationship had been suspected.

The observations also allowed scientists to determine the mass of material blasted out by the collision, which is estimated to be as much as 25 fully-loaded tractor trailer-trucks.

The findings are based on the composition of rocky dust detected by both the Subaru and Gemini 8-meter telescopes and ethane, water and carbon-based organic compounds revealed by the 10-meter W.M. Keck Observatory. The results from these Mauna Kea observations were made available today in a special segment in the journal Science highlighting results from the Deep Impact experiment.

Comet Tempel 1 was selected for the Deep Impact experiment because it orbits the Sun in a stable orbit that allows its surface to be gently baked with solar radiation. As a result, the comet has an old weathered,protective layer of dust that covers the icy material beneath, much like a snowbank builds up dirt on its surface as it melts in the springtime sunlight. The Deep Impact mission was designed to dig deep beneath this crusty exterior to learn more about the true nature of the comet’s dust and ice components. “This comet definitely had something to hide under its veneer of rock and ice and we were ready with the world’s biggest telescopes to find out what it was,” said Chick Woodward of the University of Minneapolis and part of the Gemini observing team.

The combined observations show a complex mix of silicates, water and organic compounds beneath the surface of the comet. These materials are similar to what is seen in another class of comets thought to reside in a distant swarm of pristine bodies called the Oort Cloud. Oort Cloud comets are well preserved fossils in the frozen suburbs of the solar system that have changed little over the billions of years since their formation. When they are occasionally nudged gravitationally toward the Sun they warm up and release a profuse amount of gas and dust on a one-time visit to the inner solar system..

Returning comets like Tempel 1 (known as periodic comets) were believed to have formed in a colder nursery distinctly different from the birthplaces of their cousins, the Oort Cloud comets. The evidence for two distinct “family trees” lies in their vastly different orbits and apparent composition. “Now we see that the difference may really be just superficial: only skin deep.” said Woodward. “Under the surface, these comets may not be so different after all.

This similarity indicates that both types of comets might have shared a birthplace in a region of the forming solar system where temperatures were warm enough to produce the materials observed. “It is now likely that these bodies formed between the orbits of Jupiter and Neptune in a common nursery,” said Seiji Sugita of the University of Tokyo and Subaru team member.

“Another question that the Mauna Kea telescopes were able to address is the amount of mass ejected when the comet was impacted by the chunk of copper about the size of a grand piano from the Deep Impact spacecraft,” Sugita commented. At the time of impact the spacecraft was traveling at about 23,000 miles per hour or nearly 37,000 kilometers per hour.

Because the spacecraft was unable to study the size of the crater created after it was formed, the high-resolution Mauna Kea observations provided the necessary data to get a firm estimate of the mass ejection, which was about 1000 tons. “To release this amount of material, the comet must have a fairly soft consistency,” Sugita said.

“The splash from NASA’s impact probe freed these materials and we were in the right place to capture them with the biggest telescopes on Earth,” said W.M. Keck Director Fred Chaffee. “The close collaboration among Keck, Gemini and Subaru assured that the very best science was done by the best telescopes in the world, demonstrating that the whole is often greater than the sum of its parts.”

All three of Mauna Kea’s largest telescopes observed the comet in the infrared part of the spectrum which is light that can be described as “redder than red.” The Deep Impact spacecraft was not designed to observe the comet in the mid-infrared (or thermal infrared) part of the spectrum, which is what Subaru and Gemini were able to do. The Keck observations used a near-infrared, high-resolution spectrograph. Large instruments of this sort would have been impossible to fit on the Deep Impact spacecraft.

“These observations give us the best glimpse yet at what’s under the dusty skin of a comet,” said David Harker who led the Gemini team. “Within an hour of impact, the comet’s glow was transformed and we were able to detect a whole host of fine dusty silicates propelled by a sustained gas geyser from under the comet’s protective crust. These included a large amount of olivine, similar in composition to what you would find at the beaches below Mauna Kea. This incredible data was really a gift from Mauna Kea!”

Instruments that made these observations were:

* MICHELLE (Mid-Infrared Echelle Spectrograph/Imager) on the 8-meter Fredrick C. Gillett (Gemini North) Telescope
* NIRSPEC (Near-Infrared Spectrograph) on the 10-meter on the Keck II 10-meter telescope
* COMICS (COoled Mid-Infrared Camera and Spectrograph) on the 8-meter Subaru telescope

Original Source: NAOJ News Release

What is the biggest telescope?

Posted on by Fraser Cain

Two Weather Satellites About to Launch

Artist’s concept of CloudSat and Calipso orbiting Earth. Image credit: NASA Click to enlarge
Two NASA satellites, planned for launch no earlier than Oct. 26, will give us a unique view of Earth’s atmosphere. CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (Calipso) are undergoing final preparations for launch from Vandenberg Air Force Base, Calif.

CloudSat and Calipso will provide a new, 3-D perspective on Earth’s clouds and airborne particles called aerosols. The satellites will answer questions about how clouds and aerosols form, evolve and affect water supply, climate, weather and air quality.

CloudSat and Calipso employ revolutionary tools that will probe Earth’s atmosphere. Each spacecraft carries an “active” instrument that transmits pulses of energy and measures the portion of the pulses scattered back to the instrument.

CloudSat’s cloud-profiling radar is more than 1,000 times more sensitive than typical weather radar. It can detect clouds and distinguish between cloud particles and precipitation. “The new information from CloudSat will answer basic questions about how rain and snow are produced by clouds, how rain and snow are distributed worldwide and how clouds affect the Earth’s climate,” said Dr. Graeme Stephens, CloudSat principal investigator at Colorado State University, Fort Collins, Colo.

Calipso’s polarization lidar instrument can detect aerosol particles and can distinguish between aerosol and cloud particles. “With the high resolution observation that Calipso will provide, we will get a better understanding of aerosol transport and how our climate system works,” said Dr. David Winker, Calipso principal investigator at NASA’s Langley Research Center, Hampton, Va.

The satellites will be launched into a 705-kilometer (438-mile) circular, sun-synchronous polar orbit, where they will fly in formation just 15 seconds apart as members of NASA’s “A-Train” constellation with three other Earth Observing System satellites. The A-Train includes NASA’s Aqua and Aura satellites and France’s Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with observations from a Lidar satellite.

The usefulness of data from CloudSat, Calipso and the other A-Train satellites will be much greater when combined. The combined set of measurements will provide new insight into the global distribution and evolution of clouds that will lead to improvements in weather forecasting and climate prediction.

CloudSat is managed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif. The radar instrument was developed at JPL, with hardware contributions from the Canadian Space Agency. Colorado State University provides scientific leadership and science data processing and distribution.

Other contributions include resources from the U.S. Air Force and the U.S. Department of Energy. Ball Aerospace and Technologies Corp. designed and built the spacecraft. A host of U.S. and international universities and research centers provides support to the science team. Some of these activities are contributed as partnerships with the project.

Calipso was developed through collaboration between NASA and the French Space Agency, Centre National d’Etudes Spatiales. NASA’s Langley Research Center leads the Calipso mission and provides science team leadership, systems engineering, payload mission operations, and validation, processing and archiving of data. Langley also developed the lidar instrument in collaboration with the Ball Aerospace and Technologies Corp., which developed the onboard visible camera.

NASA’s Goddard Space Flight Center, Greenbelt, Md., provides project management, system engineering support and overall program management. Centre National d’Etudes Spatiales provides a Proteus spacecraft developed by Alcatel, the imaging infrared radiometer, payload-to-spacecraft integration and spacecraft mission operations. The Institut Pierre Simon Laplace in Paris provides the imaging infrared radiometer science oversight, data validation and archival. Hampton University provides scientific contributions and manages the outreach program.

For more information on CloudSat and Calipso on the Internet, please visit http://www.nasa.gov/cloudsat and http://www.nasa.gov/calipso .

Original Source: NASA News Release