Robot to Dig Martian Arctic

Source:

http://www.space.com/scienceastronomy/080520-st-mars-lander-science.html

A soft touchdown in Mars' northern arctic plains set for Sunday is just the first step for NASA's Phoenix Mars Lander. If the dust clears, solar-power arrays deploy and all equipment checks out, Phoenix will then have some digging to do.
While its rover cousins continue to investigate the surface of the red planet (as they have since early 2004), the $462 million dollar Phoenix mission aims to see what's underneath the soil. "Our voyage is down; we dig," said Phoenix principal investigator Peter Smith of the University of Arizona.
At its landing site in the Vastitas Borealis near Mars' north pole, Phoenix is designed to scoop up samples of Martian soil, as well as the layers of rock-hard ice beneath, in the hopes of shedding light on when and how the ice formed and whether it has ever melted and moistened the surrounding soils. This information could shed light on whether this little-studied area of the planet could ever have been habitable for life, though Phoenix's mission isn't to find life itself.
"We're literally scratching the surface, and it's a stepping stone," Smith said. "If we see something that's unexpected and absolutely fascinating and interesting, I would expect NASA would want other missions, that it would go take the next step in the polar regions."
Soil and ice
The vast layers of ice underlying the Vastitas Borealis were discovered in 2002, when the Mars Odyssey orbiter detected the signature of water below the top few inches of ruddy dust that coats the planet. Phoenix will provide the first direct look at this frozen subsurface layer from its landing site at 68 degrees north latitude and 233 degrees east longitude.
"What Phoenix is trying to do is follow the water and validate what we think we discovered from orbit," said Phoenix landing site working group chairman Ray Arvidson of Washington University in St. Louis.
Phoenix's 7.7-foot (2.3-meter) robotic arm will dig down through the soil to the ice layer below, which is expected to be at about -136 degrees Fahrenheit (-93 degrees Celsius). At that temperature "the bonds [in the water] are so strong [that the ice is] as strong as a concrete sidewalk," Arvidson said.
At the end of the robotic arm is a rasp, about the size of your pinky finger, that will rotate down into the ice and kick up tiny pieces into the scoop for analysis by instruments aboard the lander.
One of the key measurements Phoenix is designed to make is the abundance of the different isotopes (which are versions of the same element with different atomic weights) of hydrogen and oxygen in the water ice. The most common form of hydrogen has no neutrons, but one of its isotopes, deuterium, has one neutron. Oxygen commonly has eight neutrons (this is called oxygen-16), but one of its stable isotopes has 10 (called oxygen-18). Phoenix's mass spectrometer will measure the ratios of the isotopes of these two elements, "and that should be a signature of the processes involved in making that ice," Arvidson said.
Here is what those details could reveal about ice on Mars: One theory is that the ice is in equilibrium with the scant amount of water vapor in Mars' atmosphere and froze out of the air and into the pore spaces between the soil grains. Because Mars' gravity is weaker than Earth's, it can only hold on to heavier elements in its atmosphere, so it has a higher ratio of deuterium and oxygen-18 to their lighter isotopes. If the mass spec examines the isotopic ratios of the water and the air "and if they're identical, it means that the water in the atmosphere is in contact, in equilibrium with the ice," Arvidson explained.
"But suppose it's a different isotopic composition — it means that ice was inplaced in some other time, when water in the atmosphere had a different isotopic composition," Arvidson told SPACE.com. "So we're trying to get at the past history and the role of water at the high latitudes."
Signs of life
The lander also is set to scoop up samples of soil near the ice layer to look for signs of potential habitability. Because the ice has been so cold for so long, "it's been in a deep-freeze, and if there are any organics, they should be very well preserved," just as food can be preserved in your freezer, Arvidson said.
The frozen ground on Mars today probably isn't too hospitable a place for life, so mission scientists aren't expecting to get to the pole and find "little green men," or even "little green microbes" — instead the lander will look for conditions that could support them.
Specifically, the instruments on Phoenix will analyze the soil to see if the water ice layer was once ever a liquid water layer.
"Liquid water changes soil, ice doesn't do much of anything," Smith explained. "Ice is like another form of rock. Nothing happens because ice is nearby — it has to melt."
So if the lander's instruments find evidence of clays, salts or carbonates — all of which are transformed by water — in the soil, that would mean that "the soil was wet with liquid water" or was blown in from somewhere else on the planet that once had liquid water, Smith explained.
In the search for signs of life on Mars, "there's not a magical formula that we're looking for," Arvidson said, but there are a few key conditions that would increase the likelihood that Mars at least at some point harbored life.
The first is the ice itself, "because water and habitability kind of go together," Arvidson said. Phoenix will also dissolve soil samples in four teacup-sized beakers that have electrodes to measure the soil's pH (level of acidity) and oxidation potential, which can affect an organism's ability to carry out certain key biochemical reactions. It will also look for certain elements (carbon, hydrogen, oxygen, phosphorus and sulfur) that go hand-in-hand with life, on Earth at least.
Gases given off when soil samples are heated in tiny ovens aboard the spacecraft will show whether any organic compounds, which could be traces of past life, are present in the soil. But scientists have to make certain that any detected organics didn't just make the trip with the lander from Earth.
"If we get a hit like that, we are going to be totally, totally, like, probably for two or three days, making sure we haven't goofed in some way," Arvidson said.
"In fact, it's really tough. If we measure organics, the first thing we think is, 'It's terrestrial; we brought it with us.' The second thing is that it's from the asteroids and comets," Smith agreed. "It would take a considerable amount of evidence before we could talk about biology."
Martian weather
When Phoenix's three-month primary mission is completed (likely in September) at the end of the northern hemisphere summer on Mars, the lander will switch modes to become a weather station.
The weather instrumentation aboard the lander, provided by the Canadian Space Agency, includes a 4-foot (1.2-meter) mast with sensors at three heights that can monitor temperature. A wind telltale at the top of the mast shows the wind direction and speed.
A probe that can measure the moisture level of soil also is designed to measure the relative humidity of the Martian air. Such measurements characterizing the atmosphere at high latitudes have never been made before, Arvidson said.
Phoenix is also equipped with a lidar (for "light detection and ranging") tool that can measure dust and ice particles in the atmosphere. The tool sends powerful laser pulses vertically into the air, which then scatter off the particles, some returning to the instrument. This information will help scientists track changes in particle abundance and learn how clouds and dust plumes move and form in the Martian atmosphere.
Mission scientists are also hoping that as summer ends and the polar ice cap expands, Phoenix will be able to watch the process. "That would be totally cool," Arvidson says, since the ice cap formation has never been observed from the surface. Scientists don't even know if the white coating observed from satellites is frost, snow or slabs of ice.
"If we're lucky, what we'll see is the accumulation of ice, water ice, and dust, and maybe even CO2 [carbon dioxide] ice," Arvidson said.
Eventually, as the sun sets (though it rises and descends in the sky each "sol," or Martian day, the sun remains about the horizon throughout the northern hemisphere summer above the arctic circle, just as it does on Earth) and the craft is encased in this advancing ice, it will end its mission for good.
Because no craft has ever ventured this far north on Mars (the closest was Viking 2's landing at 48 degrees latitude), scientists have little idea what to expect from any of the analyses Phoenix will perform. Whether they'll find signs of a muddy Martian past or organics is anybody's guess.
"I can't tell you what we're going to find, because this is really exploration and discovery," Arvidson said.
Video: The Nail-Biting Landing of Phoenix on Mars
Video: Looking for Life in All the Right Places
The Top 10 Martian Landings of All Time

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The Mouse That Roared: Pipsqueak Star Unleashes Monster Flare

Source:

http://www.sciencedaily.com/releases/2008/05/080519113218.htm

ScienceDaily (May 19, 2008) — On April 25, NASA’s Swift satellite picked up the brightest flare ever seen from a normal star other than our Sun. The flare, an explosive release of energy from a star, packed the power of thousands of solar flares. It would have been visible to the naked eye if the star had been easily observable in the night sky at the time.
The star, known as EV Lacertae, isn’t much to write home about. It’s a run-of-the-mill red dwarf, by far the most common type of star in the universe. It shines with only one percent of the Sun’s light, and contains only a third of the Sun’s mass. At a distance of only 16 light-years, EV Lacertae is one of our closest stellar neighbors. But with its feeble light output, its faint magnitude-10 glow is far below naked-eye visibility.
"Here’s a small, cool star that shot off a monster flare. This star has a record of producing flares, but this one takes the cake," says Rachel Osten, a Hubble Fellow at the University of Maryland, College Park and NASA’s Goddard Space Flight Center in Greenbelt, Md. "Flares like this would deplete the atmospheres of life-bearing planets, sterilizing their surfaces."
The flare was first seen by the Russian-built Konus instrument on NASA’s Wind satellite in the early morning hours of April 25. Swift’s X-ray Telescope caught the flare less than two minutes later, and quickly slewed to point toward EV Lacertae. When Swift tried to observe the star with its Ultraviolet/Optical Telescope, the flare was so bright that the instrument shut itself down for safety reasons. The star remained bright in X-rays for 8 hours before settling back to normal.
EV Lacertae can be likened to an unruly child that throws frequent temper tantrums. The star is relatively young, with an estimated age of a few hundred million years. The star rotates once every four days, which is much faster than the sun, which rotates once every four weeks. EV Lacertae’s fast rotation generates strong localized magnetic fields, making it more than 100 times as magnetically powerful as the Sun’s field. The energy stored in its magnetic field powers these giant flares.
EV Lacertae’s constellation, Lacerta, is visible in the spring for only a few hours each night in the Northern Hemisphere. But if the star had been more easily visible, the flare probably would have been bright enough that the star could have been seen with the naked eye for one to two hours.
The flare’s incredible brightness enabled Swift to make detailed measurements. "This gives us a golden opportunity to study a stellar flare on a second-by-second basis to see how it evolved," says Stephen Drake of NASA Goddard.
Since EV Lacertae is 15 times younger than our Sun, it gives us a window into our solar system’s early history. Younger stars rotate faster and generate more powerful flares, so in its first billion years the sun must have let loose millions of energetic flares that would have profoundly affected Earth and the other planets.
Flares release energy across the electromagnetic spectrum, but the extremely high gas temperatures produced by flares can only be studied with high-energy telescopes like those on Swift. Swift's wide field and rapid repointing capabilities, designed to study gamma-ray bursts, make it ideal for studying stellar flares. Most other X-ray observatories have studied this star and others like it, but they have to be extremely lucky to catch and study powerful flares due to their much smaller fields of view.
Red Dwarfs, Killer Flares, and Earth-Like Planets
"Data like this on the flares of red dwarfs, also known as M stars, are important not only to help up understand the nature of these flares, but also because of renewed interest in searching for Earth-like planets around M stars," explained Osten.
About 75 percent of all stars in our Galaxy are M stars, which are long-lived, stable, and burn hydrogen. Until recently, M stars have been considered poor candidates for harboring habitable planets. This was, in part, because it was thought the violent flares generated by intense magnetic activity, could erode or even blast away planetary atmospheres. This problem was seemingly heightened by the fact that habitable zone for planets around a red dwarf would be much closer than that for larger, much more radiant stars like the sun.
However, recent theoretical studies have shown that the environment of M stars might not preclude their planets from harboring life have made M stars much more interesting to astronomers. "From a detection standpoint, M stars are ideal targets in the search for habitable planets, because the smaller size of these stars makes it much easier to detect smaller orbiting planets using transit and radial-velocity techniques," Osten said.

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Part Of Universe's Missing Matter Discovered By XMM-Newton X-Ray Observatory

Source:

http://www.sciencedaily.com/releases/2008/05/080506194033.htm

ScienceDaily (May 7, 2008) — ESA’s orbiting X-ray observatory XMM-Newton has been used by a team of international astronomers to uncover part of the missing matter in the universe.

Ten years ago, scientists predicted that about half of the missing ‘ordinary’ or normal matter made of atoms exists in the form of low-density gas, filling vast spaces between galaxies.
All the matter in the universe is distributed in a web-like structure. At dense nodes of the cosmic web are clusters of galaxies, the largest objects in the universe. Astronomers suspected that the low-density gas permeates the filaments of the web.
The low density of the gas hampered many attempts to detect it in the past. With XMM-Newton’s high sensitivity, astronomers have discovered its hottest parts. The discovery will help them understand the evolution of the cosmic web.
Only about 5% of our universe is made of normal matter as we know it, consisting of protons and neutrons, or baryons, which along with electrons, form the building blocks of ordinary matter. The rest of our universe is composed of elusive dark matter (23%) and dark energy (72%).
Small as the percentage might be, half of the ordinary baryonic matter is unaccounted for. All the stars, galaxies and gas observable in the universe account for less than a half of all the baryons that should be around.
Scientists predicted that the gas would have a high temperature and so it would primarily emit low-energy X-rays. But its very low density made observation difficult.
Astronomers using XMM-Newton were observing a pair of galaxy clusters, Abell 222 and Abell 223, situated at a distance of 2300 million light-years from Earth, when the images and spectra of the system revealed a bridge of hot gas connecting the clusters.
"The hot gas that we see in this bridge or filament is probably the hottest and densest part of the diffuse gas in the cosmic web, believed to constitute about half the baryonic matter in the universe," says Norbert Werner from SRON Netherlands Institute for Space Research, leader of the team reporting the discovery.
“The discovery of the warmest of the missing baryons is important. That’s because various models exist and they all predict that the missing baryons are some form of warm gas, but the models tend to disagree about the extremes,” adds Alexis Finoguenov, a team member.
Even with XMM-Newton’s sensitivity, the discovery was only possible because the filament is along the line of sight, concentrating the emission from the entire filament in a small region of the sky. The discovery of this hot gas will help better understand the evolution of the cosmic web.
"This is only the beginning. To understand the distribution of the matter within the cosmic web, we have to see more systems like this one. And ultimately launch a dedicated space observatory to observe the cosmic web with a much higher sensitivity than possible with current missions. Our result allows to set up reliable requirements for those new missions." concludes Norbert Werner.
ESA’s XMM-Newton Project Scientist, Norbert Schartel, comments on the discovery, “This important breakthrough is great news for the mission. The gas has been detected after hard work and more importantly, we now know where to look for it. I expect many follow-up studies with XMM-Newton in the future targeting such highly promising regions in the sky.”
Adapted from materials provided by European Space Agency.

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Plan To Send A Probe To The Sun

Source:

http://www.sciencedaily.com/releases/2008/05/080502094224.htm

ScienceDaily (May 4, 2008) — The Johns Hopkins University Applied Physics Laboratory is sending a spacecraft closer to the sun than any probe has ever gone – and what it finds could revolutionize what we know about our star and the solar wind that influences everything in our solar system.

NASA has tapped APL to develop the ambitious Solar Probe mission, which will study the streams of charged particles the sun hurls into space from a vantage point within the sun’s corona – its outer atmosphere – where the processes that heat the corona and produce solar wind occur. At closest approach Solar Probe would zip past the sun at 125 miles per second, protected by a carbon-composite heat shield that must withstand up to 2,600 degrees Fahrenheit and survive blasts of radiation and energized dust at levels not experienced by any previous spacecraft.
Experts in the U.S. and abroad have grappled with this mission concept for more than 30 years, running into seemingly insurmountable technology and budgetary limitations. But in February an APL-led team completed a Solar Probe engineering and mission design study at NASA’s request, detailing just how the robotic mission could be accomplished. The study team used an APL-led 2005 study as its baseline, but then significantly altered the concept to meet challenging cost and technical conditions provided by NASA.
“We knew we were on the right track,” says Andrew Dantzler, Solar Probe project manager at APL. “Now we’ve put it all together in an innovative package; the technology is within reach, the concept is feasible and the entire mission can be done for less than $750 million [in fiscal 2007 dollars], or about the cost of a medium-class planetary mission. NASA decided it was time.”
APL will design and build the spacecraft, on a schedule to launch in 2015. The compact, solar-powered probe would weigh about 1,000 pounds; preliminary designs include a 9-foot-diameter, 6-inch-thick, carbon-foam-filled solar shield atop the spacecraft body. Two sets of solar arrays would retract or extend as the spacecraft swings toward or away from the sun during several loops around the inner solar system, making sure the panels stay at proper temperatures and power levels. At its closest passes the spacecraft must survive solar intensity more than 500 times what spacecraft experience while orbiting Earth.
Solar Probe will use seven Venus flybys over nearly seven years to gradually shrink its orbit around the sun, coming as close as 4.1 million miles (6.6 million kilometers) to the sun, well within the orbit of Mercury and about eight times closer than any spacecraft has come before.
Solar Probe will employ a combination of in-place and remote measurements to achieve the mission’s primary scientific goals: determine the structure and dynamics of the magnetic fields at the sources of solar wind; trace the flow of energy that heats the corona and accelerates the solar wind; determine what mechanisms accelerate and transport energetic particles; and explore dusty plasma near the sun and its influence on solar wind and energetic particle formation. Details will be spelled out in a Solar Probe Science and Technology Definition Team study that NASA will release later this year. NASA will also release a separate Announcement of Opportunity for the spacecraft’s science payload.
“Solar Probe is a true mission of exploration,” says Dr. Robert Decker, Solar Probe project scientist at APL. “For example, the spacecraft will go close enough to the sun to watch the solar wind speed up from subsonic to supersonic, and it will fly though the birthplace of the highest energy solar particles. And, as with all missions of discovery, Solar Probe is likely to raise more questions than it answers.”
APL’s experience in developing spacecraft to study the sun-Earth relationship – or to work near the sun – includes ACE, which recently marked its 10th year of sampling energetic particles between Earth and the sun; TIMED, currently examining solar effects on Earth's upper atmosphere; the twin STEREO probes, which have snapped the first 3-D images of explosive solar events called coronal mass ejections; and the Radiation Belt Storm Probes, which will examine the regions of energetic particles trapped by Earth’s magnetic field.
Solar Probe will be fortified with heat-resistant technologies developed for APL’s MESSENGER spacecraft, which completed its first flyby of Mercury in January and will begin orbiting that planet in 2011. Solar Probe’s solar shield concept was partially influenced by designs of MESSENGER’s sunshade.
Adapted from materials provided by Johns Hopkins University.

Fausto Intilla - www.oloscience.com

Supercomputer To Simulate Extreme Stellar Physics

Source:

http://www.sciencedaily.com/releases/2008/05/080502133106.htm

ScienceDaily (May 3, 2008) — Robert Fisher and Cal Jordan are among a team of scientists who will expend 22 million computational hours during the next year on one of the world’s most powerful supercomputers, simulating an event that takes less than five seconds.
Fisher and Jordan require such resources in their field of extreme science. Their work at the University of Chicago’s Center for Astrophysical Thermonuclear Flashes explores how the laws of nature unfold in natural phenomena at unimaginably extreme temperatures and pressures. The Blue Gene/P supercomputer at Argonne National Laboratory will serve as one of their primary tools for studying exploding stars.
“The Argonne Blue Gene/P supercomputer is one of the largest and fastest supercomputers in the world,” said Fisher, a Flash Center Research Scientist. “It has massive computational resources that are not available on smaller platforms elsewhere.”
Desktop computers typically contain only one or two processors; Blue Gene/P has more than 160,000 processors. What a desktop computer could accomplish in a thousand years, the Blue Gene/P supercomputer can perform in three days. “It’s a different scale of computation. It’s computation at the cutting edge of science,” Fisher said.
Access to Blue Gene/P, housed at the Argonne Advanced Leadership Computing Facility, was made possible by a time allocation from the U.S. Department of Energy’s Innovative and Novel Computational Impact on Theory and Experiment program. The Flash Center was founded in 1997 with a grant from the National Nuclear Security Administration’s Office of Advanced Simulation and Computing. The NNSA’s Academic Strategic Alliance Program has sustained the Flash Center with funding and computing resources throughout its history.
The support stems from the DOE’s interest in the physics that take place at extremes of concentrated energy, including exploding stars called supernovas. The Flash Center will devote its computer allocation to studying Type Ia supernovas, in which temperatures reach billions of degrees.
A better understanding of Type Ia supernovas is critical to solving the mystery of dark energy, one of the grandest challenges facing today’s cosmologists. Dark energy is somehow causing the universe to expand at an accelerating rate.
Cosmologists discovered dark energy by using Type Ia supernovas as cosmic measuring devices. All Type Ia supernovas display approximately the same brightness, so scientists could assess the distance of the exploding stars’ home galaxies accordingly. Nevertheless, these supernovas display a variation of approximately 15 percent.
“To really understand dark energy, you have to nail this variation to about 1 percent,” said Jordan, a Flash Center Research Associate.
The density of white dwarf stars, from which Type Ia supernovas evolve, is equally extreme. When stars the size of the sun reach the ends of their lives, they have shed most of their mass and leave behind an inert core about the size of the moon. “If one were able to scoop out a cubic centimeter—roughly a teaspoon—of material from that white dwarf, it would weigh a thousand metric tons,” Fisher explained. “These are incredibly dense objects.”
Type Ia supernovas are believed to only occur in binary star systems, those in which two stars orbit one another. When a binary white dwarf has gravitationally pulled enough matter off its companion star, an explosion ensues.
“This takes place over hundreds of millions of years,” Jordan said. “As the white dwarf becomes more and more dense with matter compressing on top of it, an ignition takes place in its core. This ignition burns through the star and eventually leads to a huge explosion.”
The Flash team conducts whole-star simulations on a supercomputer at Lawrence Berkeley National Laboratory in California. At Argonne, the team will perform a related set of simulations. “You can think of them as a nuclear ‘flame in a box’ in a small chunk of the full white dwarf,” Fisher said.
In the simulations at Argonne, the team will analyze how burning occurs in four possible scenarios that lead to Type Ia supernovas. Burning in a white dwarf can occur as a deflagration or as a detonation.
“Imagine a pool of gasoline and throw a match on it. That kind of burning across the pool of gasoline is a deflagration,” Jordan said. “A detonation is simply if you were to light a stick of dynamite and allow it to explode.”
In the Flash Center scenario, deflagration starts off-center of the star’s core. The burning creates a hot bubble of less dense ash that pops out the side due to buoyancy, like a piece of Styrofoam submerged in water. But gravity holds the ash close to the surface of the white dwarf. “This fast-moving ash stays confined to the surface, flows around the white dwarf and collides on the opposite side of breakout,” Jordan said.
The collision triggers a detonation that incinerates the star. There are, however, three other scenarios to consider. “To understand how the simulations relate to the actual supernovae, we have to do more than a thousand different simulations this year to vary the parameters within the models to see how the parameters affect the supernovae,” Jordan said.
Adapted from materials provided by University of Chicago.

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