2013년 5월 27일 월요일

Student-Built Robots to Race in Mock Mars Rover Challenge

What does it take to build and command a vehicle capable of exploring Mars? Ninety students from around the world are about to find out.
Next week, in a remote desert in southern Utah, 10 teams from the United States, Canada, India and Poland will compete in the annual University Rover Challenge (URC). The competition is hosted by the Mars Society, a non-profit research organization dedicated to promoting the exploration and eventual settlement of Mars.
The competition site is located at the society's Mars Desert Research Station (MDRS), a rocky barren landscape that's about as close to Martian terrain as you can get on Earth. 

Each team was allowed to spend up to $15,000 on their rovers, which can weigh no more than 50 kilograms — about 110 lbs.
On Monday (May 27), the first members of the URC team will arrive at the Research Station to start setting up, Kevin Sloan, director of the URC, told us. The competition will begin early Thursday morning as teams leave their lodgings in Hanksville, Utah (Pop. 215), and travel about seven miles along a road that dwindles to a dirt track. Over three days, teams will use their vehicles to compete in four challenges, designed to replicate the activities of NASA's rovers on Mars.
For instance, Mars rover Curiosity, now in its ninth month of a two-year mission on Mars, has recently been deployed to its second drilling site to take rock samples, analyze them for evidence of microscopic life and send the data back to NASA. Likewise, teams will guide their rovers to collect the subsurface soil samples most likely to contain photosynthetic bacteria, lichen and other bits of living material.
The specific tasks change each year, but the most difficult ones continue to be those that need rovers to do humanlike work.
"Year after year, the tasks that involve manipulation — that is to say using the robot's arm and hand to do meaningful work —  really stress the teams' systems the most," Sloan said. "Manipulation from a mobile platform is one of the biggest challenges in the robotics community."
Like NASA controllers, team members must guide their rovers via a remote connection, such as a computer in the back of a truck, as long as it's shielded so the team can't see their rovers. The URC is based on the assumption that the rovers are telerobots, which means they would be operated by astronauts on or orbiting Mars.
In addition to collecting soil, the rovers will deliver a series of packages, such as emergency supplies to "astronauts" (URC staff) in the field, fix a dust-covered solar panel (without water, of course) and finally, navigate an obstacle course that will include climbing steep grades, getting over boulders and passing through PVC pipe gates, aimed to test each rover's maneuverability.
This year's teams represent universities and colleges in Canada, India, Poland and the United States, including two-time returning champions Toronto's York University (2012 and 2009) and Oregon State (2010 and 2008).
Details about the capabilities of this year's rovers are kept under wraps by the teams. However, Sloan did tell us he expects one rover to include an unmanned aerial vehicle, i.e., a drone.
"Other than that, I don't have any insight into unique system features," Sloan said. "Like everyone else, I'm waiting to be surprised next week in the field!"

Source of Article: Space.com

Exquisite Map of Cosmos Hints at Universe's Birth

A map of the universe based on its oldest light is giving astronomers hope that they may be able to answer some of the deepest questions of the cosmos, including how it got started.
Scientists met this week at the University of California, Davis to pore over the treasure trove of data published two months ago from the European Planck spacecraft. The observatory measures what's called the cosmic microwave background— light spread across the sky that dates from soon after the Big Bang that kick-started the universe.
"We have the best map ever of the cosmic microwave background, and that shows us what the universe was like 370,000 years after the Big Bang," said Charles Lawrence, a scientist at NASA's Jet Propulsion Laboratory in California who is the lead U.S. scientist on the Planck project. Lawrence and other researchers summed up the consequences of the meeting, called the Davis Cosmic Frontiers Conferences, in a call to reporters Friday (May 24).
The cosmic microwave background (CMB) was first discovered in 1964, and since then a series of experiments, culminating in Planck, have measured it in increasing detail, providing cosmologists a direct line to test theories about the beginnings of the universe. Planck launched in 2009, and the recent data represent the product of the spacecraft's first 15.5 months of observations.
"Rarely in the history of science has there been such a triumphant transformation from really complete ignorance to really deep insights in just a few decades," said Andreas Albrecht, chair of the University of California, Davis Department of Physics.
The CMB has provided strong support for the theory of cosmic inflation, which suggests that the universe ballooned in size during a period of exponential growth within the first fraction of a second after the Big Bang. Variations in the temperature of the CMB light are thought to correspond to tiny density ripples in the universe caused by quantum fluctuations when it first formed. These ripples, in turn, gave rise to the structure we see today in the form of stars, galaxies and clusters of galaxies.
Studying the CMB's variations in detail could help scientists differentiate between various models of inflation, and answer the many unsolved puzzles remaining, such as what happened before inflation, what sparked it, and which version of inflation took place.
"If it weren't for the wonderful data, I'd be thinking maybe some of these problems are too difficult for us right now," Albrecht said. "But it's thrilling to be inspired by all this data and the tremendous success we have had with the theories so far to really plunge in and wrestle these deep questions."
Already some "anomalies" in the Planck data appear to deviate from the standard expectations, and if borne out, these deviations could point the way toward new physics, scientists say. For example, the basic picture of inflation predicts that the universe should have expanded uniformly in all directions, but the CMB's temperature variations appear to be sixed and spaced differently toward one side of the universe than the other. In addition, the variations don't seem to behave the same on small scales as they do on large scales.
"It's hard to know what to make of these anomalies," said Lloyd Knox, a University of California, Davis physicist who's leading the U.S. team inferring cosmology parameters from Planck's data. "That these are real features of the microwave background sky has really been firmed up by Planck, but how to make sense of them isn't clear, so there's some excitement about them and some people are going after this as a clue."
Ultimately, all of the scientists expressed their thrill at being able to plunge into some of the thorniest questions about the universe using the exquisite data from Planck. Right now, they said, astrophysicists have a rare opportunity to make huge leaps in progress, and the researchers consider themselves lucky to be working at this point in the history of science.
"I don't think you could do better than doing cosmology right now; it's just amazing," Albrecht said.

Source of Article: Space.com

How 3D Printers Could Reinvent NASA Space Food

A NASA-funded project that aims to transform a 3D printer into a space kitchen could one day reinvent how astronauts eat in the final frontier.
NASA officials confirmed this week that the space agency awarded $125,000 to the Austin, Texas-based company Systems and Materials Research Consultancy (SMRC) to study how to make nutritious and efficient space food with a 3D-printer during long space missions. The project made headlines this week largely because of the first item on the menu: a 3D-printed space pizza.
Future astronauts on deep-space mission will face a host of health and sustenance challenges. A roundtrip from Earth to Mars, for instance, could last several years and require thousands of meals for an astronaut crew.
"The current food system wouldn't meet the nutritional needs and five-year shelf life required for a mission to Mars or other long duration missions," NASA officials said in a statement. "Because refrigeration and freezing require significant spacecraft resources, current NASA provisions consist solely of individually prepackaged shelf stable foods, processed with technologies that degrade the micronutrients in the foods."
NASA officials said SMRC will explore whether a 3D-printed food system will be able to provide nutrient stability and a wide variety of foods from shelf stable ingredients, while minimizing waste and saving time for space crews.
Engineers at SMRC are apparently envisioning a system that can "print" dishes using layers of food powders that will have a shelf life of three decades.
"The way we are working on it is, all the carbs, proteins and macro and micro nutrients are in powder form," Anjan Contractor, a senior mechanical engineer at SMRC, told Quartz, which first reported the project. "We take moisture out, and in that form it will last maybe 30 years."
Contractor already printed chocolate and now is working on a prototype to print a pizza, according to Quartz. NASA later issued a statement about the Small Business Innovation Research phase I contract that was given to SMRC.
This initial six-month project could lead to a phase II study, but NASA officials said the technology is still years away from being tested on an actual flight.
Besides printing celestial pizza, 3D printing could have other uses in space. Also called additive manufacturing, the technology could allow astronauts to make replacement parts for spacecraft or even extraterrestrial habitats, like a lunar base.
"NASA recognizes in-space and additive manufacturing offers the potential for new mission opportunities, whether 'printing' food, tools or entire spacecraft," space agency officials said. "Additive manufacturing offers opportunities to get the best fit, form and delivery systems of materials for deep space travel."
In a separate project, NASA is planning to launch a 3D printer to the International Space Station to test space manufacturing technology for long-duration missions. That project stems from a partnership between the company Made in Space and NASA's Marshall Space Flight Center in Huntsville, Ala.
Called the 3D Printing Zero G Experiment, the test flight will send a Made in Space 3D printer to the space station in 2014 to demonstrate the feasibility of using the technology to construct spare parts and tools from raw materials on a deep-space mission.

Source of Article: Space.com

2013년 5월 21일 화요일

Extreme Solar Storm Could Cause Widespread Disruptions on Earth

If an extreme solar storm aimed at the Earth hits in just the right way, it could put interconnected electrical grids around the world at serious risk, experts say.
In addition to creating beautiful auroras, extreme solar storms could knock out a wide range of electric utilities needed to keep life in the United States and around the world functioning normally, according to presenters here at the fourth annual Electric Infrastructure Security Summit.
"What [a solar storm] can do — even if it isn't causing a continental-scale outage — it can really cause a regional blackout," said Daniel Baker, director of the Laboratory for Atmospheric and Space Physics at the University of Colorado"Imagine something like, for example, Superstorm Sandy. Imagine that kind of severe storm — but causing regional outages for weeks. Living without power really cascades and propagates in remarkable ways throughout our society."
As the sun reaches the peak in its 11-year cycle this year, scientists expect that active regions of the star — known as sunspots — will erupt, flinging streams of charged particles out into the solar system. Relatively minor storms can also create temporary radio blackouts and disrupt GPS navigation.
However, this doesn't necessarily mean that all solar eruptions will impact the Earth. Most coronal mass ejections are not aimed toward the planet, and instead shoot out harmlessly into other parts of the solar system. But once every century or so, an extreme solar storm is expected to impact the Earth, Baker told SPACE.com.  
The last documented solar storm in this category is known as the Carrington event. Particles from a powerful coronal mass ejection overloaded telegraph wires, setting paper messages on fire in 1859.
These kinds of storms from the sun are notoriously difficult to predict. Experts understand the general conditions under which solar storms occur, but it's hard to forecast just how powerful the storm will be, said Karel Schrijver, a solar scientist and fellow at Lockheed Martin.
"A [coronal mass ejection] takes two to four days to get to the Earth, so if we had more observational resources, to map its motion — and if we had some measurements of the structure of what's going to hit you — there are ways by which we can certainly improve the forecast," Schrijver told SPACE.com.
Scientists can use sun-observing satellites like NASA's Solar Dynamics Observatory to monitor, and possibly forecast, solar weather that could be heading toward the planet, Schrijver said.
"There's a lot of space to be explored in terms of computer models that are becoming ever more powerful," Schrijver added. "The heliophysics division at NASA has a wonderful fleet of observatories that looks at the space between the sun and the Earth and the Earth's environment."

Source of Article: Space.com

Alien Planets Could Shed Light on Earth's Climate Future

A Comparative Climatology Symposium held at NASA Headquarters on May 7 focused on new approaches to climate research by highlighting the similarities and contrasts between the environments of the rocky worlds Venus, Earth, Mars and Saturn’s smoggy moon Titan. 
The symposium also included discussions about exoplanets, the sun and past, present and future space missions.
John Grunsfeld, Associate Administrator for NASA’s Science Mission Directorate, said that the upcoming James Webb Space Telescope will be able to make important observations of the atmospheres of exoplanets.
He said JWST won’t be able to locate the exoplanets, only study them, but the recently selected TESS mission could act as a  planet scout for JWST targets. It is estimated that TESS will discover around 300 "super-Earth" alien planets, many of them in the habitable zone.
But the number one challenge, Grunsfeld noted, is figuring out the climate of our own planet.
Understanding climate change
Jim Green, NASA’s Planetary Science Division Director, said that one goal is to examine a variety of planetary bodies as a system, to see if there are trends or similarities. He also pointed out that from a planetary scientist’s perspective, climate change on our planet is not a new thing.
"Earth’s climate has done nothing but change," Green said. 
Green said that three Earth-observing satellites will be launched this year, and they will help us better understand how the climate is currently changing and the implications that has for our planet’s environment.
David Grinspoon, holder of the first Baruch S. Blumberg NASA/Library of Congress chair in Astrobiology, talked about Mars’ "ferocious and interesting" meteorology, and how Martian global dust storms may help unravel what happened on our planet during the K-T extinction 65 million years ago, when an asteroid hitting the Yucatan Peninsula is thought to have eradicated 75 percent of animals and plants on Earth, including the dinosaurs.
The 'Venus mafia'
As for Venus, Grinspoon said scientists believe current-day volcanism on Venus is thought to be necessary to sustain the planet’s thick clouds. He added that the active surface has eradicated most ancient rocks, preventing us from easily understanding Venus’ early history.
Grinspoon also discussed the unique climate of Titan, noting that the methane cycle on this moon of Saturn is "like Earth's hydrological cycle on steroids."
Studying the climates of Mars, Venus, Titan and even exoplanets could help us refine our climate models of the Earth. However, Grinspoon said that "clouds are the biggest uncertainty in understanding the past of Venus and predicting the future of Earth."
Tying climatology to astrobiology, Grinspoon said that our expectations of the other planets, in the absence of data, were that they'd be much more Earth-like than they actually are. We still haven’t found a planet quite like our own, although astronomers are zeroing in on exoplanets that should have habitable conditions.
But, Grinspoon said, "it may be that conditions for life's origin aren't rare, but the hard part is the persistence of habitable conditions."
Venus was a popular topic during the symposium. Roald Sagdeev, University of Maryland professor and former director of the Space Research Institute of the USSR Academy of Sciences, said during an overview of the Russian missions to Venus that "from the point of view of habitability, Venus is like having a dead body to study, which is of course very useful for learning anatomy."
David Crisp, Senior Research Scientist at the Jet Propulsion Laboratory/California Institute of Technology, said that sending weather balloons to Venus taught us a lot about atmospheric physics. And Roger Bonnet, Executive Director of the International Space Science Institute, said there was no chance for a big "flagship" mission to Venus, since the viewpoint among many amounts to "Who cares about clouds and wind on Venus, when we have so much of that on Earth? We want to see little green men!"
One participant noted the presence of "the Venus mafia" at the symposium, inferring that the focus on Earth’s "twin planet" had muscled out discussion of other places of interest. 
Habitable exoplanets
But in addition to studies of Venus and other terrestrial worlds, there was a talk about our sun and its influence on space weather, and general discussions about refining climate models, defining habitable zones, and the importance of basic research.
The participants seemed to agree that, most importantly, planetary climate studies needed to be interdisciplinary, with scientists from different fields communicating and collaborating.
Michael Meyer, lead scientist for the Mars Exploration Program at NASA Headquarters, also pointed out that we should never become complacent in our scientific understanding. For instance, he said that while climate models have not been able to make early Mars warm enough to sustain liquid water on its surface, the same can be true for models of the young Earth. 
And when it comes to understanding where a planet needs to reside in its solar system to be habitable — the so-called Goldilocks Zone where the temperature is just right for water to be liquid rather than ice or gas — he commented that "the approach [to the habitable zone] is very Goldilocks in that it's almost a fairy tale."   
Finally, Meyer noted, just when we thought we understood how planets are made, we discovered hot Jupiters and other unusual exoplanets that "turned all of our planet formation models on their head." 
"And that’s a good thing," he added.

Source of Article: Space.com

Big Meteor Explosion on Moon Shows Lunar Exploration Risks

The dramatic meteorite strike that blasted out a big crater on the moon two months ago shows just how perilous manned lunar exploration can be.
A 1-foot-wide (0.3 meters) rock slammed into the lunar surface at 56,000 mph (90,120 km/h) on March 17, creating a fresh crater 65 feet (20 m) wide. The crash caused the biggest and brightest explosion scientists have seen since they started monitoring lunar meteorite strikes in 2005.
"The flash was so bright it saturated the camera," said Bill Cooke, head of the Meteoroid Environment Office at NASA's Marshall Space Flight Center in Huntsville, Ala. The lunar blast was the equivalent of 5 tons of TNT going off, scientists said. 
Space rocks of similar size hit Earth every day or two, but our atmosphere generally burns them up completely or breaks them into small pieces that do little damage when they hit the ground. The moon lacks such a protective shield, however, and thus takes such collisions squarely on the chin.
Future manned moon missions will have to take the exposed nature of the lunar surface into account. Lunar bases could be buried underground, for example, to hide from meteorite strikes and the relatively high radiation levels at ground level (another consequence of the moon's having no appreciable atmosphere).
"Nothing like a few meters of ground to help shield you," Cooke told SPACE.com via email.
But astronauts who venture onto the surface to do exploration or science work would put themselves at risk. And relatively large space rocks like the one that hit on March 17 would not be their primary concern.
"The big risk to humans there is that posed by smaller particles (millimeter-size) capable of penetrating a spacesuit," Cooke said. "This dwarfs the risk to an outpost on the surface."
The meteorite problem on Mars would not be so serious, as the Red Planet's carbon-dioxide-dominated atmosphere gives it some level of protection.
Still, Mars' atmosphere is just 1 percent as thick as that of Earth, so many rocks manage to reach the surface. In fact, a new study estimates that about 200 meteorites slam into the Red Planet every year, most of them no bigger than 3 to 6 feet (1 to 2 m) across.
NASA is planning on sending astronauts to the vicinity of Mars by the mid-2030s, and several private organizations also have their eyes on the Red Planet.
The nonprofit Inspiration Mars Foundation, for example, aims to launch two people on a flyby mission around the Red Planet in January 2018. And the Netherlands-based nonprofit Mars One hopes to land four astronauts on the planet in 2023 as the vanguard of a permanent settlement.

Source of Article: Space.com

2013년 5월 17일 금요일

Electric Cars on Earth and Mars: How They Stack Up

Electric cars may still play second fiddle to gas-guzzlers here on Earth, but they've dominated the Martian driving scene for more than a decade.
NASA's tiny Sojourner rover hit the red dirt in 1997, followed by the golf-cart-size twins Spirit and Opportunity in 2004. And last August, the 1-ton Curiosity rover dropped in to determine whether Mars could ever have supported microbial life.
All three generations of six-wheeled NASA rovers have used electric power systems of various design and complexity to find their way around the Red Planet.
"On Mars, there was no other option," said Curiosity strategic uplink lead Nagin Cox, of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "There isn't a gas station."

From solar to nuclear power
Most electric cars on the road today rely on lithium-ion batteries, which must be plugged in and recharged on a regular basis. Mars rovers are millions of miles from the nearest electrical outlets or charging station, so they take a different tack.
The 25-lb. (11.5 kilograms) Sojourner generated electricity using solar arrays, with a set of three small, nonrechargeable lithium-thionyl chloride batteries serving as backup.
The much larger Spirit and Opportunity also rely primarily on solar panels. Unlike Sojourner, however, they sport rechargeable lithium-ion batteries, which allow them greater functionality when the sun isn't shining.
Curiosity, on the other hand, is powered by a radioisotope thermoelectric generator (RTG), which converts the heat generated by the radioactive decay of plutonium-238 into electricity. RTGs have powered many NASA deep-space probes over the decades, including the twin Voyager spacecraft, which are knocking on the door of interstellar space.
Like Spirit and Opportunity, the SUV-size Curiosity also employs two rechargeable lithium-ion batteries to give it extra juice when needed.
"The batteries enable Curiosity's power subsystem to meet peak power demands of rover activities when the demand temporarily exceeds the onboard multi-mission radioisotope thermoelectric generator (MMRTG) steady output level," the Curiosity team wrote in a mission update shortly before the rover's nerve-wracking landing, which saw it lowered to the Martian surface on cables by a rocket-powered sky crane.
Improving technology on Earth and Mars
As battery technology improves, electric cars on Earth are getting better and better, with greater power and increased range. The baseline configuration of Tesla's Model S, for example, can go 208 miles (335 kilometers) on one charge and accelerate from 0 to 60 mph (97 km/h) in 5.9 seconds, according to the company.
Mars rovers keep improving with each iteration as well. Sojourner carried one science instrument and three cameras, and it lasted 83 days on Mars before conking out.
Spirit and Opportunity have six engineering cameras and three science cameras, along with three other scientific instruments.
While both rovers were originally tasked with three-month prime missions to seek signs of past water activity on Mars, Spirit was just declared dead in 2011. Opportunity is still going strong after more than nine years on the Red Planet, and just broke the American record for longest distance traveled on the surface of another world.
"One thing we've definitely learned is, never bet against Opportunity," Cox, who also has experience working on Spirit and Opportunity's mission, told SPACE.com.
Curiosity is the biggest and most advanced Mars rover yet, NASA officials say. It sports 10 different scientific instruments and 17 cameras, and its RTG could keep powering the robot for a decade or more.
Curiosity and its kin are built for science, not speed, so they can't keep up with the Model S or any other electric car on the market today. Curiosity's top speed on flat, hard ground is 1.5 inches per second, which works out to 0.09 mph (0.14 km/h).
Because they're so slow and steady, Mars rovers also can't compete with terrestrial electrical vehicles (EVs) in terms of range. Sojourner traveled a total of 330 feet (100 meters), while Spirit put 4.80 miles (7.73 km) on its odometer.
Opportunity has covered 22.20 miles (35.76 km) thus far, just short of the all-time record for most distance traveled by a robot on the surface of another world. The Soviet Union's Lunokhod 2 rover traveled 23 miles (37 km) on the moon in 1973.
Curiosity has covered just 2,300 feet (700 m) since its arrival on the Red Planet. But the rover should embark on an epic 5-mile (8 km) drive to the base of the mysterious 3.4-mile-high (5.5 km) Mount Sharp in the next month or so, mission scientists say.

Driving forward
Cox and her husband are electric-car advocates and aficionados. They own a Nissan Leaf and share a Tesla Roadster with relatives, and they once had an EV1 — the first mass-produced electric vehicle of the modern era, which General Motors manufactured in the late 1990s.
Electricity will power Mars rovers for the foreseeable future. Cox expressed hope that EVs will become a bigger part of the driving picture here on Earth as well, helping humanity avoid the worst consequences of climate change.
"I think EVs are helping us learn how to coexist on the Earth without using it up, at the same time that they're helping us extend our reach to Mars and explore places that we couldn't reach without those technologies," she said.

Source of Article : space.com

2013년 5월 15일 수요일

NASA May Launch Donated Spy Satellite Telescope to Mars

One of the two spy satellite telescopes that recently fell into NASA's lap may eventually make its way to the Red Planet.
The space agency is currently mulling potential uses for the two space telescopes, which were donated by the National Reconnaissance Office and are comparable in size and appearance to NASA's venerable Hubble Space Telescope (HST).
Some scientists have proposed sending one of the powerful telescopes to Mars orbit, where it could look both up and down, giving researchers great views of the Red Planet's surface as well as targets in the outer solar system and beyond.
"We're probably not going to get a replacement for HST with UV/visible [light] and a big telescope for use at Mars," said Alfred McEwen of the University of Arizona, leader of the proposed Mars Orbiting Space Telescope, or MOST. "So this is trying to do two things with one mission."
An unexpected gift
The two donated telescopes were apparently built for a National Reconnaissance Office program calledFuture Imagery Architecture, which was terminated in 2005.
NASA announced in June 2012 that it had acquired the instruments, which are designed to have a much wider field of view than Hubble, despite sporting Hubble-like 8-foot-wide (2.4 meters) main mirrors.
In November, the space agency asked scientists to suggest potential uses for the NRO scopes, which are basically just primary and secondary mirrors, with no instruments attached. More than 60 serious proposals came flooding in, 33 of which — including MOST — were presented in early February at the Study on Applications of Large Space Optics (SALSO) workshop in Huntsville, Ala.
A powerful tool at Mars
As it's currently envisioned, MOST would have three main science instruments — an imaging spectral mapper, a high-resolution imager and an ultraviolet spectrometer — allowing it to make a broad range of detailed observations.
The mapper would have a spatial resolution of 0.7 feet (0.21 m) per pixel at an orbiting altitude of 250 miles (400 kilometers), McEwen said. That's about 100 times better than the resolution achieved by a similar instrument aboard NASA's Mars Reconnaissance Orbiter (MRO), which has been circling the Red Planet since 2006.
So MOST could give scientists unprecedented looks at intriguing Mars landforms, potentially shedding light on the planet's past and present ability to host life as we know it.
"This would be fantastic for things like the recurring slope lineae, which we think may be present-day flow of water on Mars," McEwen told SPACE.com. "And for ancient Mars as well — you're getting mineralogic information at much higher spatial resolution, and now you're seeing things at the scale that you can investigate in the field with rovers."
MOST's imaging instrument would be able to photograph small areas with a resolution of 3.1 inches (8 centimeters) per pixel — about four times better than MRO's HiRise instrument (which McEwen leads as principal investigator).
These capabilities could help NASA plan out future activities on the Red Planet — for example, by pinning down the best places to send a sample-return mission or set up a manned base. MOST would also likely carry a UHF antenna to relay data from Mars rovers and landers to Earth, further aiding operations at the Red Planet, team members say.
"When pointed at Mars, MOST can significantly advance our understanding of the past and present habitability of Mars, both from direct science observations and by providing critical support to robotic and potential human exploration on the surface of Mars or its moons," McEwen and his colleagues wrote in their SALSO presentation.
Looking beyond Mars
MOST would also be built to look up and out, beyond the Red Planet and its two tiny moons.
The telescope's UV spectrometer is envisioned to be similar to that of the Hubble Space Telescope. But MOST likely wouldn't be able to study extremely distant objects as well as the famous HST, because installing a Hubble-like guidance and navigation system that allows a prolonged lock on such faint targets would raise the price tag significantly, McEwen said.
Instead, MOST may be optimized to view planets and moons in the outer solar system.
"We decided to emphasize bright targets, so mostly solar system targets — monitoring Jupiter, Saturn, Uranus, Neptune atmospheres, monitoring volcanism on [Jupiter's moon] Io and cloud patterns on [Saturn's moon] Titan," McEwen said. "There's an interesting variety of things you could do in planetary science with it."
A Mars-orbiting space telescope would be outside of Earth's geocorona, a wispy but luminous region of our planet's extreme outer atmosphere. And there are other advantages of placing an instrument around the Red Planet as well, McEwen and his colleagues say.
"MOST can provide a larger baseline for stereoscopic viewing of targets combined with Earth-based telescopes," they write in the SALSO presentation. "A greater range of viewing angles for targets in the outer solar system are possible from Mars than from Earth. The inner asteroid belt can be viewed from significantly closer range."
Getting to Mars
MOST would likely be far too heavy to send to Mars using traditional chemical propulsion. So a solar electric system, like the one powering NASA's asteroid-studying Dawn probe, would be employed once the telescope reached space.
Solar electric propulsion is slow but steady. It would probably take MOST 2.5 years to reach Mars, then another 2.17 years to spiral down to its final orbit, McEwen said, noting that the telescope could make science observations during the journey.
The MOST team didn't give a cost estimate for the mission. But another group, led by Zachary Bailey of NASA's Jet Propulsion Laboratory in Pasadena, Calif., estimated that it would cost about $900 million to mount a sort of de-scoped version of MOST, called High Resolution Surface Science at Mars.
High Resolution Surface Science at Mars, which Bailey's team presented at the SALSO workshop, would stare down at Mars using two main science instruments. The mission would launch in April 2018 and arrive at Mars nearly two years later, also using solar electric propulsion.
McEwen said MOST would probably need a minimum of five years before it would be ready to launch.
No decisions yet
But any talk of timelines is preliminary at the moment, because MOST, High Resolution Surface Science at Mars and the other ideas presented at SALSO are in a holding pattern.
NASA won't examine these concepts seriously until learning the results of a separate study looking into using one of the NRO scopes for the proposed Wide-Field Infrared Survey Telescope (WFIRST), a high-priority NASA mission that would probe the mysteries of dark energy and hunt for exoplanets.
Source of Article : space.com

Jaw-Dropping Views of Night Sky and Earth Win Photo Contest

Eye-popping images of celestial wonders shining over equally stunning Earth views have won the top spots in the 2013 International Earth and Sky Photo Contest, competition organizers say.
The contest, the third annual event held by the landscape astrophotography group The World at Night (TWAN), aims to raise awareness about the importance of dark skies free of light pollution. It honors photos that show both the Earth and sky in all their glory.
"The amazing number of eye-catching entries from across the world tells how public attention to night sky is growing as well as interest to sky photography, and we are very pleased if TWAN has a role on this increasing awareness," Babak Tafreshi, TWAN director and one of the contest founders, said in a statement. 
More than 700 entries were submitted to the contest, which was open to photographers of any age anywhere in the world. Winners were chosen in two categories: "Beauty of the Night Sky" and "Against the Lights."
The first emphasizes the wonder of the heavens, while the second highlights the problem of light pollution — the excess artificial light from cities that not only wastes energy and disrupts ecosystems, but obscures the comparatively dim light of the stars from view.

The top prize in the beauty category went to Stephane Vetter of France, who captured a panoramic photo in March 2013 of the aurora borealis and the Milky Way over the "Waterfall of the Gods" in Iceland. The first prize in the lights category was won by to Andreas Max Böckle of Austria for his photo showing the constellation Orion shining dimly over the glowing lights of the city of Salzburg, with the majestic Alps visible on the horizon.
Other winners include a stunning view of the stars over Canyon Lake in Arizona captured by is Zach Grether of the United States, and a photo of the Milky Way glowing in the sky over Reunion Island in the Indian Ocean, taken by Reunion Island resident Luc Perrot (a picture described by judge David Malin as having "perfect composition, color, focus. Outstanding!").
The contest aimed to honor photographs that portray the genuine beauty of nature, with minimal editing or exaggeration through retouching.

"A large number of the images with excellent composition and idea didn't reach the winners because of poor editing or over-cooked processing where the natural colors of night sky were altered by extreme white balance shift or applying too much color saturation," Tafreshi said. "While editing is of course essential in any style of photography specially when dealing with challenging low-light condition, according to the contest criteria entries should be 'gently' edited so they preserve the natural-looking sky and the originality of a photograph (compared to digital art)."
Prizes for the winners included expensive camera equipment, binoculars, and star tracking tools.

Source of Article : space.com

Huge Solar Flares Keep Erupting from Busy Sunspot

An overachieving sunspot on the surface of the sun unleashed its fourth major solar flare in two days late Tuesday (May 14), a solar storm that may deal Earth a glancing blow, space weather experts say.
The active sunspot AR1748 roared to life Tuesday night releasing an X-class solar flare — the strongest type the sun can experience — that peaked at 9:48 p.m. EDT (0148 May 15 GMT), according to NOAA's Space Weather Prediction Center in Boulder, Colo. The flare came after a relative lull in activity from sunspot AR1748, which fired off three monster X-class solar flares within a 24-hour period between Sunday and Monday.
In a morning update, NOAA space weather officials said they are studying this latest solar flare from AR1748 to see if it coincided with an eruption of super-hot solar plasma known as a coronal mass ejection, or CME. Such explosions can unleash huge waves of charged solar material streaking out into space at millions of miles per hour. 
"Too early to know if a CME occurred. If one did, it may just glance the Earth's magnetic field, given its off-center location still," SWPC officials said. "Forecasters are pondering that one."

Public outreach officials with NASA's sun-watching Solar Dynamics Observatory released a photo of Tuesday night's X-class flare via the mission's Camilla mascot Twitter page, and suggested a CME event did occur.
Sunspot AR1748 is about twice the size of Earth and is currently located on the sun's extreme left side, so it is not directly facing our planet.
The solar storm Tuesday night registered as an X1.2 solar flare, making it the weakest in the four-flare series from sunspot AR1748. The stormy activity began late Sunday (May 12) when the sun fired off an X1.7 flare. Two more flares followed on Monday, an X2.8 flare at midday and an even stronger X3.2 that night.
According to solar astrophysicist C. Alex Young at NASA's Goddard Space Flight Center, the sunspot will likely be facing Earth by this weekend.
"In a couple of days, it will be far enough onto the disk that any CMEs that we got would probably have some impact on Earth," Young told SPACE.com Tuesday.
When aimed directly at Earth, X-class solar flares can pose a risk to astronauts and satellites in orbit, as well as interfere with radio, GPS and other communications signals. X-class flares and more moderate, but still intense, M-class sun storms can also supercharge Earth's auroras to create spectacular northern lights displays.
The sun is currently in an active period of its 11-year solar weather cycle and is expected to reach its peak activity later this year. The current sun weather cycle, called Solar Cycle 24, began in 2008.
Scientists have been tracking the sun's solar flares and other space weather events since they were first discovered in 1843. Today, a fleet of international spacecraft keep constant watch on the sun's activity.

Source of Article : space.com

Planet-Hunting Kepler Spacecraft Suffers Major Failure, NASA Says

The planet-hunting days of NASA's prolific Kepler space telescope, which has discovered more than 2,700 potential alien worlds to date, may be over.
The second of Kepler's four reaction wheels — devices that allow the observatory to maintain its position in space — has failed, NASA officials announced Wednesday (May 15).
If one or both of those failed wheels cannot be brought back, the telescope likely cannot lock onto target stars precisely enough to detect orbiting planets, scientists have said.
Staring at stars
The $600 million Kepler spacecraft spots exoplanets by flagging the tiny brightness dips caused when they pass in front of their host stars from the instrument's perspective. The mission's main goal is to determine how common Earth-like alien planets are throughout the Milky Way galaxy.
Kepler needs three functioning reaction wheels to stay locked onto its more than 150,000 target stars. The observatory had four wheels when it launched in March 2009 — three for immediate use, and one spare.
One wheel (known as number two) failed in July 2012, giving Kepler no margin for error. And now wheel number four has apparently given up the ghost as well, after showing signs of elevated friction for the past five months or so.
"This is something that we've been expecting for a while, unfortunately," NASA science chief John Grunsfeld told reporters today.
Grunsfeld is a former astronaut who flew on five space shuttle missions, including three that serviced or upgraded NASA's Hubble Space Telescope in Earth orbit. But in-space repair is not an option for Kepler, which circles the sun rather than Earth and is currently about 40 million miles (64 million kilometers) from our planet.
A new mission?
The Kepler team is not taking the wheel failures lying down. Engineers will try to recover number two and number four, perhaps by turning the wheels to power through any deterioration in their mechanisms, team members have said.
"I wouldn't call Kepler down and out just yet," Grunsfeld said.
If this and other measures don't work, however, Kepler will probably get a new mission, likely one that emphasizes scanning the heavens over its previous "point and stare" operations. 
The team is already thinking about what a new scanning mode might be able to accomplish. Researchers are also trying to figure out ways to conserve fuel, so Kepler can keep operating for as long as possible if it needs to start using its thrusters to help point at targets.
Kepler's legacy
Whatever the future holds for Kepler, the mission will go down in history as an incredible success, researchers say.
While just 132 of Kepler's 2,700-odd planet candidates have been confirmed by follow-up observations to date, mission scientists estimate that more than 90 percent will end up being the real deal.
Further, the telescope's discoveries have allowed researchers to take an unprecedented, systematic look at worlds beyond our solar system — learning, for instance, that small, rocky planets are much more common throughout the Milky Way galaxy than gas giants like Saturn or Jupiter, at least in close-in orbits.
"Kepler has opened up the next set of questions in exoplanets," said Paul Hertz, astrophysics director at NASA Headquarters in Washington, D.C.
"Before we flew Kepler, we didn't know that Earth-sized planets in habitable zones were common throughout our galaxy," Hertz added. "We didn't know that virtually every star in the sky had planets around them. Now we know that."
Kepler also outlasted its prime mission life of 3.5 years; it has been working on an extended mission that takes it through at least fiscal year 2016.
While the observatory may not spot any more exoplanets from here on out, that doesn't mean the flood of Kepler discoveries will slow down anytime
"We've really only sort of looked at half the dataset so far. We just haven't had the time and the processing hours to go through it all," Kepler deputy project manager Charlie Sobeck, of NASA's Ames Research Center in Moffett Field, Calif., told SPACE.com late last month.
Once Kepler stops finding planets, he added, "the scientific output of the mission would continue for at least another year or two before you would see a dropoff."

Source of Article : space.com

2013년 5월 13일 월요일

Skylab's Grave: Remains of 1st American Space Station in Australia

NASA will celebrate the 40th anniversary of the launch of Skylab, America's first space station, on Tuesday (May 14), but you might be surprised where this icon of U.S. human spaceflight ended up.
After hosting rotating astronaut crews from 1973-1974, the Skylab space station eventually fell back to Earth in pieces that landed in Australia. Now, decades later, many of those pieces are on display at Australian museums, offering a fascinating glimpse into America's first stab at living in space.
From May 1973 to February 1974, Skylabsaw a trio of three-man crews take up residence aboard the outpost, before it was abandoned with the plan of possibly using the space shuttle (then under development) to reactivate the laboratory. But with no way to reboost Skylab to a higher orbit to keep it aloft, and delays in getting the shuttle off the ground , the space station re-entered the Earth’s atmosphere over the southern Indian Ocean in 1979, with pieces landing inland along the south coast of Western Australia. 
The mostly uncontrolled re-entry was a media sensation at the time, with newspapers offering prizes for the first debris found and to persons impacted by falling pieces. NASA's attempt at sending Skylab into the Indian Ocean, out of harm's way, proved only somewhat successful, and the spacecraft entered several minutes earlier than predicted, slightly off course.
Several large chunks and dozens of smaller pieces of Skylab survived the fiery plunge through the atmosphere and impacted the ground in the Australian outback over a large swath centered around the community of Balladonia on the Nullarbor Plain. The largest pieces included the oxygen tanks designed to keep the crew alive during their stays.
Skylab on display
Visitors can almost miss Skylab. Tucked away in a large display case in a small city museum, the remains of what fell from the sky on July 11, 1979, can be found in Esperance, a port town with less than 10,000 inhabitants located 450 miles from Perth, which is the only major city in the western half of the sparsely populated country. Esperance was directly under the path of Skylab's re-entry.
On the outside, the corrugated metal walls and roof of the museum have the appearance of four long warehouses. That's because the Esperance Municipal Museum, founded in 1976 on the site of a former railroad yard, is composed of converted train equipment sheds.
From the main road along the waterfront in Esperance, a small blue and yellow sign hung on the side of the building is all that denotes it as a "museum," and a larger hanging billboard makes note of the main attraction inside: "In 1979, a spaceship crashed over Esperance. We fined them $400 for littering." A stamp next to it reads, "PAID IN FULL."
It's true. The local government slapped NASA with a comical $400 bill for the cleanup, though the U.S. space agency never officially paid up. However, on the 30th anniversary of the crash in 2009, a radio host for Highway Radio in California and Nevada used his program to raise the funds and put a formal end to the complaint. The paycheck now hangs above the remains.
Spacecraft remains
Around the front of the museum, a large model of the space station sits at a sharp angle atop a pedestal. A plaque on the side describes the space station and what happened along this lonely coastline a few decades ago.
Inside, most of what remains of Skylab can be found in a large Plexiglas-enclosed display case. The largest oxygen tank sits on the floor adjacent to it, wrapped in plastic. Inside the case, the largest intact pieces are displayed at center. These include the space station's storage freezer for food and other items, a water tank, nitrogen spheres for the station’s attitude control system thrusters and a piece of what is identified as a portion of the hatch the astronauts would have crawled through during their visits. Many smaller pieces of debris are laid out around the larger chunks, each labeled and identified where possible.
Several news articles and photographs circle the case, including photos showing the actual re-entry taken by locals and one featured in a National Geographic story from October 1979. The oversized check created by the Nevada radio station, which was used to pay the litter fine, sits proudly above it, and a proclamation from Barstow proclaiming July 13, 2009, as "Shire of Esperance/Skylab Day" lies mounted on a plaque alongside a key to the city.
Portions of the debris were sent elsewhere to be displayed, such as in the United States and Sydney. And it is possible that other pieces of debris remain in the remote outback, still waiting to be found.

If you visit Skylab
If you are visiting Western Australia, the Esperance Municipal Museum is located on James Street, between the waterfront Esplanade and Dempster Street. There is a $4 admission fee. Allow 30 minutes if your goal is to see Skylab only.
Another of the large oxygen tanks that survived Skylab's fall to Earth is on display at the U.S. Space & Rocket Center in Huntsville, Ala. The Powerhouse Museum in Sydney also a portion of a titanium sphere in its collection, but it is not believed to be on display right now.

Source of Article : space.com

Budget Cuts May Hinder Discovery of 1st Alien Earth

Astronomers are closer than ever to finding a true alien Earth, though the process may be slowed by budget cuts, scientists told members of Congress Thursday (May 9).
Officials from NASA, the National Science Foundation and the SETI (Search for Extraterrestrial Intelligence) Institute gave testimony to the House Science, Space and Technology Committee about the state of exoplanet research, saying researchers were closing in on planets around other stars that are the same size and distance from their suns as Earth.
"Within the next few years, we will have the privilege of answering this age-old question: In the universe, is there anywhere else like home?" said Laurance Doyle, principal investigator for the Center for the Study of Life in the Universe at the SETI Institute.
Astronomers have already found more than 800 planets orbiting distant stars. Most of them are large gas giants or worlds a bit bigger than ours called Super Earths. A few, though, are small enough to be rocky, and some are almost Earth-like. Within the coming months and years, scientists hope to find a terrestrial planet that could host liquid water.
"The next step for detecting life in the universe will be most likely biomarkers," Doyle said, referring to elements such as oxygen detected in the atmospheres of alien planets that might indicate the presence of living organisms on its surface. "Oxygen is indicative of plant life, possibly animal life, and maybe even intelligent life. It could be that the first detection of extraterrestrial life may be forests."
Yet observing biomarkers probably requires newer, larger telescopes than those currently available — a daunting prospect, given dwindling federal budgets for science.
"There's no question the budget environment has caused us to make some tough choices," John Grunsfeld, associate administrator of NASA's Science Mission Directorate, told members of Congress. "We're very fortunate that we have high-value observatories on orbit. One of the things we have to prioritize is, what are we going to keep operating on orbit?"
Older telescopes may have to be shut down due to a lack of funds, and the development of newer tools may be delayed, he said. For example, because of budget cuts, NASA has had to push back the start of the new Transiting Exoplanet Survey Satellite, also known as TESS, by about six months.
The National Science Foundation (NSF), which funds ground-based telescopes, faces similar difficulties.
"Some of the new observatories are more expensive to operate than the older observatories we used to have," said James Ulvestad, director of NSF's Division of Astronomical Sciences. "In order to operate those new tools, what sometimes has to give in the short term is the research grants to individual investigators."
For example, he said, the NSF has invested significantly in the new ALMA telescope in Chile (ALMA stands for Atacama Large Millimeter/submillimeter Array), which is a joint project among North America, Europe and Asia. Yet the NSF's budget woes mean it might not have enough money to give adequate grants to U.S. researchers applying for telescope time at ALMA.
"If we're not able to fund out investigators to do the research, some of the best exoplanet science done with that telescope might be done by our international partners, and not by our own investigators," Ulvestad said.
Many members of Congress expressed excitement for alien-planet research, and sympathy for the fiscal challenges the science agencies faced.
"Until the American people can help us address the entire piece of the federal spending pie, people who depend on discretionary spending are going to continually feel pinched, which is problematic," said Research Subcommittee Chairman Larry Bucshon, R-Ind. He asked the scientists how to communicate the value of their research to his constituents. "What can I tell people why what you're doing is important to the American people?"
"Investments in NASA, the NSF, in basic research, is really the investment in our future, and it's not an abstract thing," Grunsfeld, a former astronaut, responded. Money spent developing high-tech instruments for NASA telescopes, for example, stimulates the industrial innovations that are at the core of our country's prosperity, he said. "If we start cutting back on the basic research, on trying to solve very hard problems … we'll just start losing ground on the kinds of innovations that drive our economy."

Source of Article : space.com

Beautiful Plankton Blooms Seen from Space

As weather warms up off the coast of France, blooms of plankton have once again begun to form, creating a beautiful, multicolored swirl visible from space.
NASA's Terra and Aqua satellites acquired these images of the colorful blooms on April 20 and May 4, according to  the NASA Earth Observatory. On the later date, a noticeably larger bloom occurred, fueled by nutrient runoff from French rivers and warmer temperatures in the Bay of Biscay.
Phytoplankton blooms provide food for a whole host of creatures, from zooplankton (small drifting animals) to whales. Through photosynthesis, the blooms harness the energy of the sun and turn carbon dioxide into sugars. Sometimes, however, they can cause problems: certain species of phytoplankton can form so-called red tides and produce neurotoxins that affect marine mammals as well as humans. And when they get too big, the blooms can create dead zones as the algae sinks and decomposes, consuming oxygen.
The blooms can also have beneficial environmental effects. According to a study published last summer in the journal Science, phytoplankton blooms absorb about one-third of the carbon dioxide humans emit into the air each year through burning fossil fuels.
Various pigments produce the colors of the phytoplankton blooms. For example, a type of algae calledCoccolithophores makes a calcium-containing shell that creates a milky appearance, according to the Earth Observatory.

Source of Article : space.com

'Einstein's Planet': New Alien World Revealed by Relativity

Einstein's special relativity has proven more useful than ever, as scientists have now used it to discover an alien planet around another star. 
The newfound world — nicknamed "Einstein's planet" by the astronomers who discovered it — is the latest of more than 800 planets known to exist beyond our solar system, and the first to be found through this method.
The planet, officially known as Kepler-76b, is 25 percent larger than Jupiter and weighs about twice as much, putting it in a class known as "hot Jupiters." The world orbits a star located about 2,000 light-years from Earth in the constellation Cygnus.

The researchers capitalized on subtle effects predicted by Albert Einstein's special theory of relativity to find the planet. The first is called the "beaming" effect, and occurs when light from the parent star brightens as its planet tugs it a nudge closer to Earth, and dims as the planet pulls it away. Relativistic effects cause light particles, called photons, to pile up and become focused in the direction of the star's motion.
"This is the first time that this aspect of Einstein's theory of relativity has been used to discover a planet," research team member Tsevi Mazeh of Tel Aviv University in Israel said in a statement.
Additionally, gravitational tides from the orbiting planet caused its star to stretch slightly into a football shape, causing it to appear brighter when its wider side faces us, revealing more surface area. Finally, the planet itself reflects a small amount of starlight, which also contributed to its discovery.
"We are looking for very subtle effects," said team member David Latham of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "We needed high quality measurements of stellar brightnesses, accurate to a few parts per million."
The researchers used data from NASA's Kepler spacecraft, which provided the extremely detailed observations necessary. While Kepler was designed to hunt for alien planets, it normally does so using the transit method, which looks for stars that dim periodically as planets pass in front of them.
"This was only possible because of the exquisite data NASA is collecting with the Kepler spacecraft," said study leader Simchon Faigler of Tel Aviv University.
The other most popular planet-hunting tactic is called the wobble method, and searches for slight signs of movement in stars' radial velocities caused by tugging planets.
The new Einstein-based method is best for larger worlds, and is currently incapable of finding Earth-sized planets, the scientists said. Still, it offers some benefits, as it does not require high-precision measurements of a star's velocity, or for a star and its planet to align perfectly as viewed from Earth — the two main drawbacks of the most common methods.
"Each planet-hunting technique has its strengths and weaknesses. And each novel technique we add to the arsenal allows us to probe planets in new regimes," said Avi Loeb, also from the Center for Astrophysics.

Source of Article : space.com

2013년 5월 2일 목요일

Search for E.T. Should Extend Beyond 'Alien Earths,' Astronomer Says

Scientists searching for signs of life beyond our solar system should keep an open mind, for planets very different than Earth may well be habitable, a prominent researcher says.
While it may seem natural to zero in on "alien Earths," such a narrow focus would exclude many potentially life-supporting exoplanets, whose diversity continues to astound astronomers, says Sara Seager of MIT.
And researchers can't afford to be so picky, she adds, since they'll be able to get in-depth looks at just a handful of alien worlds for the foreseeable future.
"The number of planets that we're going to be able to see in our lifetime — and look at their atmospheres for signs of life— is so small that we're forced to be open-minded," Seager told SPACE.com.
Seager discusses exoplanet habitability in a review article published online today (May 2) in the journal Science.
A dazzling diversity of alien worlds
Scientists discovered the first alien planet around a sunlike star in 1995. Since then, the tally has grown to more than 700 (or more than 800, depending on whose list is consulted), with thousands more candidates waiting to be confirmed by follow-up observations.
Some of these alien worlds are broadly similar to planets in our own solar system. But many others are truly alien — enormous "hot Jupiters" that whip around their parent stars at extremely close range, for example, or "rogue planets" that cruise through the cold depths of space alone, with no parent star.
"If there is one important lesson from exoplanets, it is that anything is possible within the laws of physics and chemistry," Seager writes in the Science article. "Planets of almost all masses, sizes and orbits have been detected, illustrating not only the stochastic nature of planet formation but also a subsequent migration through the planetary disk from the planet’s place of origin."
Intriguingly, a number of planets have been spotted orbiting within the so-called "habitable zone" — that just-right range of distances from a star where liquid water is possible on a world's surface. (Water is required for life as we know it here on Earth and has thus spurred astrobiologists to "follow the water" on other planets, Seager writes.)
Just where this habitable zone lies for each planet depends on a number of factors, most crucially its host star's brightness and the planet's atmospheric makeup.
"It's really all about the greenhouse gases," Seager told SPACE.com. "The greenhouse gases are like a blanket that moderates the temperature at the surface."
Extending the habitable zone
The conventional definition of the habitable zone assumes a roughly Earth-like atmosphere, dominated by nitrogen, carbon dioxide and water vapor. But the huge diversity of alien worlds argues for a new way of thinking, writes Seager, who literally wrote the book on exoplanet atmospheres ("Exoplanet Atmospheres: Physical Processes," Princeton University Press, 2010).
For example, large and/or chilly alien worlds could conceivably hang onto their gaseous molecular hydrogen, which long ago escaped from small planets such as Earth, Venus and Mars.
Hydrogen is a powerful greenhouse gas that could make liquid water possible on a number of worlds far beyond the outer edge of the traditional habitable zone — and perhaps even on seemingly frigid rogue planets, Seager writes.
Similarly, the habitable zone may extend inward, toward the host star, on "dry" rocky planets whose atmospheres have much less water vapor than Earth's does. So it's best to consider alien planets' potential to support life individually, on a case-by-case basis, Seager says.
Looking for life
Seager and others stress that a better understanding of exoplanet habitability is key to the next phase of the alien life hunt, which seeks to search promising candidates' atmospheres for water vapor and gases that may have been produced by life.
Astronomers have already scanned the air of a few dozen planets using NASA's Hubble Space Telescope and other instruments, Seager said. But those were hot Jupiters with big, puffy atmospheres — relatively easy targets that aren't intriguing from an astrobiological perspective.
Scientists plan to do the same with smaller, potentially habitable worlds soon, Seager said. They'll use the Transiting Exoplanet Survey Satellite, which NASA recently approved for a 2017 launch, to identify promising candidates relatively close to Earth. Then NASA's James Webb Space Telescope (which is scheduled to blast off in 2018) will follow up, getting an in-depth look at these worlds' air.
Though JWST is designed to be incredibly powerful, the $8.8 billion instrument will probably only be able to investigate the atmospheres of exoplanets that lie within a few tens of light-years from Earth, Seager added.
Seager said she hopes her review article in Science helps her fellow astronomers make the most of this small pool of observable candidates.
"I hope it gets people to realize that so many types of worlds could be habitable, and that our chance of finding one is higher when we accept that," she told SPACE.com.

Source of Article : space.com