Voyager 2 at 12,000 Days still returning data about the giant outer planets

NASA's plucky Voyager 2 spacecraft has hit a long-haul operations milestone today (June 28) -- operating continuously for 12,000 days. For nearly 33 years, the venerable spacecraft has been returning data about the giant outer planets, and the characteristics and interaction of solar wind between and beyond the planets. Among its many findings, Voyager 2 discovered Neptune's Great Dark Spot and its 450-meter-per-second (1,000-mph) winds.

The two Voyager spacecraft have been the longest continuously operating spacecraft in deep space. Voyager 2 launched on August 20, 1977, when Jimmy Carter was president. Voyager 1 launched about two weeks later on Sept. 5. The two spacecraft are the most distant human-made objects, out at the edge of the heliosphere -- the bubble the sun creates around the solar system. Mission managers expect Voyager 1 to leave our solar system and enter interstellar space in the next five years or so, with Voyager 2 on track to enter interstellar space shortly after that.

Having traveled more than 21 billion kilometers (13 billion miles) on its winding path through the planets toward interstellar space, the spacecraft is now nearly 14 billion kilometers (9 billion miles) from the sun. A signal from the ground, traveling at the speed of light, takes about 12.8 hours one-way to reach Voyager 2.

Voyager 1 will reach this 12,000-day milestone on July 13, 2010 after traveling more than 22 billion kilometers (14 billion miles). Voyager 1 is currently more than 17 billion kilometers (11 billion miles) from the sun.

The Voyagers were built by JPL, which continues to operate both spacecraft. Caltech manages JPL for NASA.

Pavilion Lake Research Project

The Pavilion Lake Research Project (PLRP), conducted in British Columbia, Canada, is a multi-disciplinary science and exploration mission to explain the origin of freshwater microbialites. NASA conducts analog missions at Pavilion Lake because the extreme, remote location will provide a challenging setting to test and develop research and exploration methods. Collecting microbialite samples will help improve techniques for future space exploration missions and scientific research.

Far Side of the Moon that is Never Seen from Earth

Tidal forces between the moon and the Earth have slowed the moon' rotation so that one side of the moon always faces toward our planet. Though sometimes improperly referred to as the "dark side of the moon," it should correctly be referred to as the "far side of the moon" since it receives just as much sunlight as the side that faces us. The dark side of the moon should refer to whatever hemisphere isn't lit at a given time. Though several spacecraft have imaged the far side of the moon since then, LRO is providing new details about the entire half of the moon that is obscured from Earth. The lunar far side is rougher and has many more craters than the near side, so quite a few of the most fascinating lunar features are located there, including one of the largest known impact craters in the solar system, the South Pole-Aitken Basin. The image highlighted here shows the moon's topography from LRO's LOLA instruments with the highest elevations up above 20,000 feet in red and the lowest areas down below -20,000 feet in blue.

Cave on Mars

Using the camera on NASA's Mars Odyssey orbiter, 16 seventh-graders at Evergreen Middle School in Cottonwood, Calif., found lava tubes with one pit that appears to be a skylight to a cave. Mars Odyssey has been orbiting the Red Planet since 2001, returning data and images of the Martian surface and providing relay communications service for Mars Rovers Spirit and Opportunity.

The students in Dennis Mitchell's science class were examining Martian lava tubes as their project in the Mars Student Imaging Program offered by NASA and Arizona State University. According to the university, the imaging program allows students in upper elementary grades through to college students to participate in Mars research by having them develop a geological question to answer. The students actually command a Mars-orbiting camera to take an image to answer their question. Since MSIP began in 2004, more than 50,000 students have participated.

"The students developed a research project focused on finding the most common locations of lava tubes on Mars," Mitchell said. "Do they occur most often near the summit of a volcano, on its flanks or the plains surrounding it?"

The feature, on the slope of an equatorial volcano named Pavonis Mons, appears to be a skylight in an underground lava tube. Similar 'cave skylight' features have been found elsewhere on Mars, but this is the first seen on this volcano.

The students subsequently submitted the site as a candidate for imaging by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. HiRISE can image the surface at about 30 centimeters (12 inches) per pixel, which may allow a look inside the hole in the ground.

"It gives the students a good understanding of the way research is conducted and how that research can be important for the scientific community. This has been a wonderful experience," Mitchell said."

Three new crew members Join Expedition 24

Three new crew members arrived at the International Space Station joining Expedition 24. Flight Engineers Fyodor Yurchikhin, Doug Wheelock and Shannon Walker docked the Soyuz TMA-19 to the aft end of the Zvezda service module Thursday at 6:21 p.m. EDT.

At 8:52 p.m. the hatches were opened between the station and the Soyuz spacecraft. The new crew joined Commander Alexander Skvortsov and Flight Engineers Tracy Caldwell Dyson and Mikhail Kornienko and began safety briefings and familiarization activities.

Johnson Space Center Director Mike Coats and NASA Spaceflight Administrator Bill Gerstenmaier were in Russia and offered their congratulations to the new station crew members. Family, friends and co-workers of the crew also offered their best wishes during a live video conference shortly after hatch opening.

Before the Soyuz TMA-19 arrived, the station crew shifted its sleep schedule to greet the new arrivals. The six-member crew slept in on Friday and will take a half day off on Saturday before beginning orientation activities onboard the orbiting laboratory.

Algae: A New Way to formulate Biodiesel

I have been working on soybean and other vegetable-based biodiesel projects for a long time. Yet, after I read a story about algae and oil from algae, in my mind, I became convinced that algae is the most promising feedstock for biodiesel.

Algae--"seaweeds" in Latin--were some of the first plant-like organisms on Earth. They are photosynthetic, like land plants, and we consider them to be "simple" because they lack the many distinct organs found in land plants.

Because some algae species are oil rich, the amount of oil we can collect from them is hundreds of times greater than the amount of oil that can be collected from an equal amount of a traditional, plant-based, biodiesel feedstock like soybeans.

Algae can also grow in places away from farmlands and forests, minimizing the damage caused to ecosystems and food-chains.

In my opinion, such factors make algae oil the most promising candidate for producing biodiesel in quantities large enough to entirely replace petroleum-based transportation fuel in the United States, and a powerful solution for sustainable energy development.

Currently, most biodiesel is made from soybean oil. In order to quickly convert soybean oil into biodiesel, a catalyst needs to be used. Catalysts are compounds that make chemical reactions happen more quickly than they would otherwise. For example, a catalyst could make a chemical reaction happen in an hour instead of three days.

There are many different types of catalysts. The type used to make biodiesel from soybean oil is a liquid. This means that when the chemical reaction is finished, the catalyst is mixed in with all the reaction products--the biodiesel and any byproducts made during the reaction. To make a marketable fuel product, the catalyst has to be separated from the reaction products, a process that takes a lot of work and energy and produces undesirable waste.

This reaction to convert soybean oil to biodiesel takes place in a "batch" reactor, which looks like a large pot. In a batch reactor, only a certain amount of product can be made at a time. For example, a small batch reactor could make 10 gallons of biodiesel in an hour. After that hour, the reactor would have to be stopped so that the biodiesel and byproducts can be removed. Then, more soybean oil and catalyst would be added, and the reaction would start all over again. This type of reactor is not very good for making large amounts of biodiesel.

I have spent a lot of time studying algae and have learned a great deal about algae growth, extraction and conversion to biodiesel. In my opinion, the amount of algae oil that will be available for biodiesel production will eventually be much larger than the amount of soybean oil available.

If the liquid catalyst and batch reactor are used to change the algae oil into biodiesel, even more work and energy would be needed to separate the reaction products from the catalyst. Giant facilities with many large reactors would have to be built, and a large amount of waste would be produced. The energy and environmental benefits would be lost.

Fortunately, there are other types of catalysts and reactors. My doctorate is in chemical engineering and I have been working in the catalysis field for a long time. My background on heterogeneous (multiple component) catalysts and fixed-bed reactor engineering led me to a new catalytic approach for the algae oil biodiesel production.

Sponsored by the National Science Foundation (NSF), I worked with my colleagues at United Environment & Energy (UEE) to develop a solid catalyst and a special reactor that can convert algae oil into biodiesel.

I spend most of my day working with other scientists and technicians on experiment design, execution and data analysis.

In the system we created, instead of using a large pot, like a batch reactor, we use a reactor that is a hollow tube filled with a solid catalyst. The algae or soybean oil flows through the tube, and the reaction to make biodiesel happens as the oil flows over the catalyst. The solid catalyst stays in the tube, so it is already separated from the biodiesel and byproducts--no extra work or energy is needed!

Also, the reactor can produce biodiesel continuously. It does not need to be stopped and re-started like a batch reactor, so it can make a lot more biodiesel in a given amount of time than the batch reactor can produce.

In addition, the solid catalyst does not need to be replaced very often-- the liquid catalyst would have to be replaced every time the batch reactor is emptied--so no waste streams are produced. The cost is much lower, and the tube reactor is smaller than batch reactors, so it can be moved from one place to another.

I believe that using this solid catalyst and tube reactor can help to quickly replace petroleum diesel with biodiesel, and in the process, decrease the energy consumed during production, thereby reducing the overall environmental impact.

For Phase I of our NSF project, we had to successfully prove that our solid catalyst and tube reactor can work and determine optimal tube reactor configurations and operating conditions. Currently, we are using algae oil samples supplied from algae producers, but we have just started a new project with our partners to grow algae and extract oil from it.

Next, we are working on testing the stability of the algae biodiesel--and increasing its resistance to oxidation, if necessary--so that the fuel can be used in diesel engines.

After those tests are complete, we will concentrate on scaling up this solid catalyst and reactor system to a larger size so that more biodiesel can be produced.

All About Black Holes

Black Hole

A black hole is a region of space whose gravitational force is so strong that nothing can escape from it. A black hole is invisible because it even traps light. The fundamental descriptions of black holes are based on equations in the theory of general relativity developed by the German-born physicist Albert Einstein. The theory was published in 1916.

Characteristics of black holes

The gravitational force is strong near a black hole because all the black hole's matter is concentrated at a single point in its center. Physicists call this point a singularity. It is believed to be much smaller than an atom's nucleus.

The surface of a black hole is known as the event horizon. This is not a normal surface that you could see or touch. At the event horizon, the pull of gravity becomes infinitely strong. Thus, an object can exist there for only an instant as it plunges inward at the speed of light.

Astronomers use the radius of the event horizon to specify the size of a black hole. The radius of a black hole measured in kilometers equals three times the number of solar masses of material in the black hole. One solar mass is the mass (amount of matter) of the sun.

No one has yet discovered a black hole for certain. To prove that a compact object is a black hole, scientists would have to measure effects that only a black hole could produce. Two such effects would be a severe bending of a light beam and an extreme slowing of time. But astronomers have found compact objects that are almost certainly black holes. The astronomers refer to these objects simply as "black holes" in spite of the small amount of uncertainty. The remainder of this article follows that practice.

Formation of black holes

According to general relativity, a black hole can form when a massive star runs out of nuclear fuel and is crushed by its own gravitational force. While a star burns fuel, it creates an outward push that counters the inward pull of gravity. When no fuel remains, the star can no longer support its own weight. As a result, the core of the star collapses. If the mass of the core is three or more solar masses, the core collapses into a singularity in a fraction of a second.

Galactic black holes

Most astronomers believe that the Milky Way Galaxy -- the galaxy in which our solar system is located -- contains millions of black holes. Scientists have found a number of black holes in the Milky Way. These objects are in binary stars that give off X rays. A binary star is a pair of stars that orbit each other.

In a binary system containing a black hole, that object and a normal, visible star orbit one another closely. As a result, the black hole strips gas from the normal star, and the gas falls violently toward the black hole. Friction between the gas atoms heats the gas near the event horizon to several million degrees. Consequently, energy radiates from the gas as X rays. Astronomers have detected this radiation with X-ray telescopes.

Astronomers believe that a number of binary star systems contain black holes for two reasons: (1) Each system is a source of intense and variable X rays. The existence of these rays proves that the system contains a compact star -- either a black hole or a less compact object called a neutron star. (2) The visible star orbits the compact object at such a high velocity that the object must be more massive than three solar masses.

Supermassive black holes

Scientists believe that most galaxies have a supermassive black hole at the center. The mass of each of those objects is thought to be between 1 million and 1 billion solar masses. Astronomers suspect that supermassive black holes formed several billion years ago from gas that accumulated in the centers of the galaxies.

There is strong evidence that a supermassive black hole lies at the center of the Milky Way. Astronomers believe this black hole is a radio-wave source known as Sagittarius A* (SgrA*). The clearest indication that SgrA* is a supermassive black hole is the rapid movement of stars around it. The fastest of these stars appears to orbit SgrA* every 15.2 years at speeds that reach about 3,100 miles (5,000 kilometers) per second. The star's motion has led astronomers to conclude that an object several million times as massive as the sun must lie inside the star's orbit. The only known object that could be that massive and fit inside the star's orbit is a black hole.

Scientists Suggests Water Content of Moon's Interior Underestimated

NASA-funded scientists estimate from recent research that the volume of water molecules locked inside minerals in the moon’s interior could exceed the amount of water in the Great Lakes here on Earth.

Scientists at the Carnegie Institution’s Geophysical Laboratory in Washington, along with other scientists across the nation, determined that the water was likely present very early in the moon’s formation history as hot magma started to cool and crystallize. This finding means water is native to the moon.

“For over 40 years we thought the moon was dry,” said Francis McCubbin of Carnegie and lead author of the report published in Monday's Online Early Edition of the Proceedings of the National Academy of Sciences. “In our study we looked at hydroxyl, a compound with an oxygen atom bound with hydrogen, and apatite, a water-bearing mineral in the assemblage of minerals we examined in two Apollo samples and a lunar meteorite.”

McCubbin’s team utilized tests which detect elements in the parts per billion range. Combining their measurements with models that characterize how the material crystallized as the moon cooled during formation, they found that the minimum water content ranged from 64 parts per billion to 5 parts per million. The result is at least two orders of magnitude greater than previous results from lunar samples that estimated water content of the moon to be less than 1 parts per billion.

"In this case, when we talk about water on the moon, we mean water in the structural form hydroxyl,” said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington. “This is a very minor component of the rocks that make up the lunar interior.”

The origin of the moon is now commonly believed to be the result of a Mars-sized object that impacted the Earth 4.5 billion years ago. This impact put a large amount of material into Earth’s orbit that ultimately compacted to form the moon. The lunar magma ocean that is thought to have formed at some point during the compacting process, began to cool. During this cooling, water either escaped or was preserved as hydroxyl molecules in the crystallizing minerals.

Previous studies found evidence of water both on the lunar surface and inside the moon by using respectively, remote sensing data from the Indian spacecraft Chandrayaan-1 and other lunar sample analysis. Carnegie researchers looked within crystalline rocks called KREEP (K for potassium; REE, for rare Earth elements; and P for phosphorus). These rocks are a component of some lunar impact melt and basaltic rocks.

“Since water is insoluble in the main silicates that crystallized, we believed that it should have concentrated in those rocks,” said Andrew Steele of Carnegie and co-author of the report. “That’s why we selected KREEP to analyze.”

The identification of water from multiple types of lunar rocks that display a range of incompatible trace element signatures indicates that water may be at low concentrations but ubiquitous within the moon's interior, potentially as early as the time of lunar formation and magma ocean crystallization.

“It is gratifying to see this proof of the hydroxyl contents in lunar apatite,” said lunar scientist Bradley Jolliff of Washington University in St. Louis. “The concentrations are very low and, accordingly, they have been until recently nearly impossible to detect. We can now finally begin to consider the implications - and the origin - of water in the interior of the moon.”

The research was funded by the NASA Astrobiology, Mars Fundamental Research, and the Lunar Advanced Science and Exploration Research programs in NASA’s Planetary Division in Washington.

NASA Helps in Upcoming Asteroid Mission Homecoming

Artist's concept of the Hayabusa spacecraft (left) and sample return capsule This artist's concept depicts the Hayabusa spacecraft (left) and sample return capsule (right) entering the atmosphere over South Australia.

The space and astronomy worlds have June 13 circled on the calendar.

That's when the Japan Aerospace Exploration Agency (JAXA) expects the sample return capsule of the agency's technology demonstrator spacecraft, Hayabusa, to boomerang back to Earth. The capsule, along with its mother ship, visited a near-Earth asteroid, Itokawa, five years ago and has logged about 2 billion kilometers (1.25 billion miles) since its launch in May 2003.

With the return of the Hayabusa capsule, targeted for June 13 at Australia's remote Woomera Test Range in South Australia, JAXA will have concluded a remarkable mission of exploration -- one in which NASA scientists and engineers are playing a contributing role.

"Hayabusa will be the first space mission to have made physical contact with an asteroid and returned to Earth," said Tommy Thompson, NASA's Hayabusa project manager from the Jet Propulsion Laboratory in Pasadena, Calif. "The mission and its team have faced and overcome several challenges over the past seven years. This round-trip journey is a significant space achievement and one which NASA is proud to be part of."

Launched May 9, 2003, from the Kagoshima Space Center, Uchinoura, Japan, Hayabusa was designed as a flying testbed. Its mission: to research several new engineering technologies necessary for returning planetary samples to Earth for further study. With Hayabusa, JAXA scientists and engineers hoped to obtain detailed information on electrical propulsion and autonomous navigation, as well as an asteroid sampler and sample reentry capsule.

The 510-kilogram (950-pound) Hayabusa spacecraft rendezvoused with asteroid Itokawa in September 2005. Over the next two-and-a-half months, the spacecraft made up-close and personal scientific observations of the asteroid's shape, terrain, surface altitude distribution, mineral composition, gravity, and the way it reflected the sun's rays. On Nov. 25 of that year, Hayabusa briefly touched down on the surface of Itokawa. That was only the second time in history a spacecraft descended to the surface of an asteroid (NASA's Near Earth Asteroid Rendezvous-Shoemaker spacecraft landed on asteroid Eros on Feb. 12, 2001). Hayabusa marked the first attempt to sample asteroid surface material.

The spacecraft departed Itokawa in January 2007. The road home for the technology demonstrator has been a long one, with several anomalies encountered along the way. But now the spacecraft is three days away from its home planet, and the Australian government, working closely with JAXA, has cleared the mission for landing. A team of Japanese and American navigators is guiding Hayabusa on the final leg of its journey. Together, they calculate the final trajectory correction maneuvers Hayabusa's ion propulsion system must perform for a successful homecoming.

"We have been collaborating with the JAXA navigators since the launch of the mission," said Shyam Bhaskaran, a member of JPL's Hayabusa navigation team. "We worked closely with them during the descents to the asteroid, and now are working together to guide the spacecraft back home."

To obtain the data they need, the navigation team frequently calls upon JAXA's tracking stations in Japan, as well as those of NASA's Deep Space Network, which has antennas at Goldstone, in California's Mojave Desert; near Madrid, Spain; and near Canberra, Australia. In addition, the stations provide mission planners with near-continuous communications with the spacecraft to keep them informed on spacecraft health.

"Our task is to help advise JAXA on how to best get a spacecraft traveling at 12.2 kilometers per second (27,290 miles per hour) to intersect a very specific target point 200 kilometers (120 miles) above the Earth," said Bhaskaran. "Once that is done, and the heat shield of the sample return capsule starts glowing from atmospheric friction, our job is done."

While atmospheric entry may be the end of the line for the team that has plotted the spacecraft's every move for the past 2 billion kilometers, NASA's involvement continues for the craft's final 200 kilometers (120 miles), to the surface of the Australian Outback. A joint Japanese-U.S. team operating on the ground and in the air will monitor this most critical event to help retrieve the capsule and heat shield.

"This is the second highest velocity re-entry of a capsule in history," said Peter Jenniskens, a SETI Institute scientist at NASA's Ames Research Center in Moffett Field, Calif. "This extreme entry speed will result in high heating rates and thermal loads to the capsule's heat shield. Such manmade objects entering with interplanetary speed do not happen every day, and we hope to get a ringside seat to this one."

Jenniskens is leading an international team as it monitor the final plunge of Hayabusa to Earth using NASA's DC-8 airborne laboratory, which is managed and piloted by a crew from NASA's Dryden Flight Research Center, Edwards, Calif. The DC-8 flies above most clouds, allowing an unfettered line of sight for its instrument suite measuring the shock-heated gas and capsule surface radiation emitted by the re-entry fireball.

The data acquired by the high-flying team will help evaluate how thermal protection systems behave during these super-speedy spacecraft re-entries. This, in turn, will help engineers understand what a sample return capsule returning from Mars would undergo. The Hayabusa sample return capsule re-entry observation will be similar to earlier observations by the DC-8 team of NASA's Stardust capsule return, and the re-entry of the European Space Agency's ATV-1 ("Jules Verne") automated transfer vehicle.

Soon after the sample return capsule touches down on the ground, Hayabusa team members will retrieve it and transport it to JAXA's sample curatorial facility in Sagamihara, Japan. There, Japanese astromaterials scientists, assisted by two scientists from NASA and one from Australia, will perform a preliminary cataloging and analysis of the capsule's contents.

"This preliminary analysis follows the basic protocols used for Apollo moon rocks, Genesis and Stardust samples," said Mike Zolensky, a scientist at NASA's Astromaterials Research and Exploration Science Directorate at the Johnson Space Center, Houston. "If this capsule contains samples from the asteroid, we expect it will take a year to determine the primary characteristics of the samples, and learn how to best handle them. Then the samples will be distributed to scientists worldwide for more detailed analysis."

"The Japanese and NASA engineers and scientists involved in Hayabusa's return from asteroid Itokawa are proud of their collaboration and their joint accomplishments," said Thompson. "Certainly, any samples retrieved from Itokawa will provide exciting new insights to understanding the early history of the solar system. This will be the icing on the cake, as this mission has already taught us so much. "

NASA Expanding Tests of Star Wars

You won’t find any light sabers on the International Space Station, but you will find a trio of “droids” that look a lot like what any self-respecting science fiction fan remembers as a Star Wars “remote.”

That’s the tricky little device that Luke Skywalker used to hone his light-saber skills before he went up against Darth Vader and the rest of the evil empire.

But instead of being used for light-saber practice, the droids on the space station are being used to test automated rendezvous and formation flying in zero-gravity. And soon, there may be a host of other things the droids will be used to test as their capabilities and uses are expanded and made available for National Laboratory and other uses.

Known officially as Synchronized Position, Hold, Engage and Reorient Experimental Satellites, or SPHERES, the droids have been on the station since 2006. Astronauts have conducted more than 20 experiment sessions with them, and are on tap to conduct many more. Each SPHERES droid is self-contained with power, propulsion, computing and navigation equipment. Together, they are testing techniques that could lead to advancements in automated dockings, satellite servicing, spacecraft assembly and emergency repairs.

Those techniques can be tested in computer simulations on Earth, but the space station is the only place they can be tested under sustained microgravity conditions. So far, the tests have all occurred in the safety of the station’s interior, but in the future upgraded SPHERES satellites may venture outside the station as well.

In 1999, Massachusetts Institute of Technology (MIT) professor David Miller showed the movie Star Wars to his students on their first day of class. After the scene where Skywalker spars with a floating droid “remote,” Miller stood up and pointed: "I want you to build me some of those."

So they did. With support from the Department of Defense and NASA, Miller's undergraduates built five working droids. Three of them are on the station now.

“What is happening,” explained Miller, SPHERES’ principal investigator, “is that DARPA, who owns the facility on orbit, is transferring it to NASA.”

NASA, in turn, plans to make the capability available to other U.S. government agencies, schools, commercial concerns and students to expand the pool of ideas for how to test and use these bowling ball-sized droids.

Someone who has first-hand microgravity experience with the droids is Greg Chamitoff, who spent six months on the station as a member of the Expedition 17 and 18 crews, and was a co-investigator for the original SPHERES experiment.

“It was really incredible to be able to watch the SPHERES fly around in real-time following the logic of my algorithms right in front of me,” Chamitoff said. “As free-flying robots, these SPHERES are pretty amazing. There’s no other test bed where you can do this kind of research and development in 3-D. You can simulate it in a computer, but to do it in zero-G, and 3-D, that’s a unique capability.”

NASA's Summer Of Innovation Kicks Off Thursday

NASA kicks off its Summer of Innovation initiative at the agency’s Jet Propulsion Laboratory on Thursday, June 10. Through the program, NASA will engage thousands of middle school students and teachers in stimulating math and science-based education programs. About 250 middle school students will be on hand for the kickoff festivities, which include a live NASA TV program with NASA Administrator Charles Bolden, a visit to the facility where the next Mars rover is being built and several hands-on, educational activities.

What is Consuming Hydrogen and Acetylene on Saturn's moon Titan?

Two new papers based on data from NASA's Cassini spacecraft scrutinize the complex chemical activity on the surface of Saturn's moon Titan. While non-biological chemistry offers one possible explanation, some scientists believe these chemical signatures bolster the argument for a primitive, exotic form of life or precursor to life on Titan's surface. According to one theory put forth by astrobiologists, the signatures fulfill two important conditions necessary for a hypothesized "methane-based life."

One key finding comes from a paper online now in the journal Icarus that shows hydrogen molecules flowing down through Titan's atmosphere and disappearing at the surface. Another paper online now in the Journal of Geophysical Research maps hydrocarbons on the Titan surface and finds a lack of acetylene.

This lack of acetylene is important because that chemical would likely be the best energy source for a methane-based life on Titan, said Chris McKay, an astrobiologist at NASA Ames Research Center, Moffett Field, Calif., who proposed a set of conditions necessary for this kind of methane-based life on Titan in 2005. One interpretation of the acetylene data is that the hydrocarbon is being consumed as food. But McKay said the flow of hydrogen is even more critical because all of their proposed mechanisms involved the consumption of hydrogen.

"We suggested hydrogen consumption because it's the obvious gas for life to consume on Titan, similar to the way we consume oxygen on Earth," McKay said. "If these signs do turn out to be a sign of life, it would be doubly exciting because it would represent a second form of life independent from water-based life on Earth."

To date, methane-based life forms are only hypothetical. Scientists have not yet detected this form of life anywhere, though there are liquid-water-based microbes on Earth that thrive on methane or produce it as a waste product. On Titan, where temperatures are around 90 Kelvin (minus 290 degrees Fahrenheit), a methane-based organism would have to use a substance that is liquid as its medium for living processes, but not water itself. Water is frozen solid on Titan's surface and much too cold to support life as we know it.

The list of liquid candidates is very short: liquid methane and related molecules like ethane. While liquid water is widely regarded as necessary for life, there has been extensive speculation published in the scientific literature that this is not a strict requirement.

The new hydrogen findings are consistent with conditions that could produce an exotic, methane-based life form, but do not definitively prove its existence, said Darrell Strobel, a Cassini interdisciplinary scientist based at Johns Hopkins University in Baltimore, Md., who authored the paper on hydrogen.

Strobel, who studies the upper atmospheres of Saturn and Titan, analyzed data from Cassini's composite infrared spectrometer and ion and neutral mass spectrometer in his new paper. The paper describes densities of hydrogen in different parts of the atmosphere and the surface. Previous models had predicted that hydrogen molecules, a byproduct of ultraviolet sunlight breaking apart acetylene and methane molecules in the upper atmosphere, should be distributed fairly evenly throughout the atmospheric layers.

Strobel found a disparity in the hydrogen densities that lead to a flow down to the surface at a rate of about 10,000 trillion trillion hydrogen molecules per second. This is about the same rate at which the molecules escape out of the upper atmosphere.

"It's as if you have a hose and you're squirting hydrogen onto the ground, but it's disappearing," Strobel said. "I didn't expect this result, because molecular hydrogen is extremely chemically inert in the atmosphere, very light and buoyant. It should 'float' to the top of the atmosphere and escape."

Strobel said it is not likely that hydrogen is being stored in a cave or underground space on Titan. The Titan surface is also so cold that a chemical process that involved a catalyst would be needed to convert hydrogen molecules and acetylene back to methane, even though overall there would be a net release of energy. The energy barrier could be overcome if there were an unknown mineral acting as the catalyst on Titan's surface.

The hydrocarbon mapping research, led by Roger Clark, a Cassini team scientist based at the U.S. Geological Survey in Denver, examines data from Cassini's visual and infrared mapping spectrometer. Scientists had expected the sun's interactions with chemicals in the atmosphere to produce acetylene that falls down to coat the Titan surface. But Cassini detected no acetylene on the surface.

In addition Cassini's spectrometer detected an absence of water ice on the Titan surface, but loads of benzene and another material, which appears to be an organic compound that scientists have not yet been able to identify. The findings lead scientists to believe that the organic compounds are shellacking over the water ice that makes up Titan's bedrock with a film of hydrocarbons at least a few millimeters to centimeters thick, but possibly much deeper in some places. The ice remains covered up even as liquid methane and ethane flow all over Titan's surface and fill up lakes and seas much as liquid water does on Earth.

"Titan's atmospheric chemistry is cranking out organic compounds that rain down on the surface so fast that even as streams of liquid methane and ethane at the surface wash the organics off, the ice gets quickly covered again," Clark said. "All that implies Titan is a dynamic place where organic chemistry is happening now."

The absence of detectable acetylene on the Titan surface can very well have a non-biological explanation, said Mark Allen, principal investigator with the NASA Astrobiology Institute Titan team. Allen is based at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Allen said one possibility is that sunlight or cosmic rays are transforming the acetylene in icy aerosols in the atmosphere into more complex molecules that would fall to the ground with no acetylene signature.

"Scientific conservatism suggests that a biological explanation should be the last choice after all non-biological explanations are addressed," Allen said. "We have a lot of work to do to rule out possible non-biological explanations. It is more likely that a chemical process, without biology, can explain these results - for example, reactions involving mineral catalysts."

"These new results are surprising and exciting," said Linda Spilker, Cassini project scientist at JPL. "Cassini has many more flybys of Titan that might help us sort out just what is happening at the surface."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL.

How First Stars are Formed

When you picture a galaxy in your mind's eye, it's often a spiral with magnificent structure--long, swirling, milky-white arms of stars and gas.

Lowell Observatory astronomer Deidre Hunter has spent most of the last 17 years methodically studying galaxies that you might not expect--small, diffuse galaxies: the dwarf irregulars--to learn all she can about star formation and what that can tell her colleagues and herself about the birth of the first stars after the Big Bang.

In a National Science Foundation- (NSF) funded project called LITTLE THINGS--for Local Irregulars That Trace Luminosity Extremes (LITTLE) and The HI Nearby Galaxy Survey (THINGS) --Hunter's team is mapping the gasses in these diffuse, enigmatic galaxies to discern the many processes of star formation.

"Star formation in dwarfs today is similar to star formation right after the Big Bang," Hunter said. "Stars form out of clouds of gas. Our quest is to figure out what the molecular clouds in these irregular galaxies are, and the processes that form stars."

The LITTLE THINGS team is closely studying 41 dwarf-irregular galaxies through the lens of numerous data sets. And the galaxies are small, relatively speaking. One, DDO 75, has 1/3500 the mass of the Milky Way. Another, Leo T, was recently discovered in the Local Group of galaxies, the closest neighbors to our own Milky Way.

"Leo T is comparable in brightness to a large star cluster that contains several million stars; in contrast, the Milky Way contains about 300 billion stars," Hunter said. Some of the galaxies in our sample area are not much brighter than a large star cluster."

The process of star formation is very inefficient. Some 50 to 90 percent of the gas present in star-forming molecular clouds, including the gas in the tiny irregular galaxies, remains after stars form.

"This produces the nebulae," Hunter said. "They are like signposts that say, 'massive stars are found here.' In a general sense, it's like weather clouds on Earth. You need these molecular clouds that form out of the ubiquitous atomic hydrogen gas to precipitate stars."

Hunter added that there are probably multiple processes going on, which adds to the complexity and time-intensive nature of the LITTLE THINGS study. In the dwarf galaxies, there's star-induced star formation. There's also turbulence. "It's not just density, but also the motions of the gas," Hunter says.

The data sets Hunter and her colleagues are using include optical-wavelength data Hunter already collected and analyzed using research telescopes at Lowell's Anderson Mesa facility near Flagstaff, Ariz. But some of the new, key data are in radio wavelengths, and they come from NSF's Very Large Array (VLA) located west of Socorro, N.M.

In May 2007, Hunter was invited to give a talk at the VLA. Afterwards, a scientist with the facility suggested she put in a large proposal, that is, a proposal for a large amount of VLA telescope time. She and her team had been unsuccessful in previous smaller requests for the needed hours, but this time, the team was rewarded: about 400 hours to study a subsample of dwarf galaxies that represent a range of characteristics.

One of Hunter's collaborators, Lowell predoctoral student Megan Jackson, is looking at the motions of the stars, their velocities and their rotation. Fellow Lowell predoc Hongxin Zhang is looking closely at existing ultraviolet and optical data sets from the galaxies, helping define their star-formation histories.

Zhang has been limited with his current sets of infrared data, so he is embarking on an observing program using a special instrument called Mimir attached to the 1.8-meter Perkins Telescope at Anderson Mesa, also at Lowell. The Perkins is operated through a partnership with Boston University, and Mimir is a powerful, $2.5-millon infrared instrument built by a team led by Dan Clemens of Boston University.

As for the massive amount of VLA radio data, much has to be collected, sorted and analyzed. Kim Herrmann, a Lowell Observatory postdoctoral fellow and part of the LITTLE THINGS team, is reducing the VLA data.

"When Kim came to Flagstaff, she had never dealt with radio interferometric data," Hunter said. "But she quickly came up to speed and has now become a local expert. She has calibrated more LITTLE THINGS data than any other person on the team, and she is exactly the kind of person we need on the team. Right now, we're in this 'grunge' phase of the project; it is very tedious. If all goes well, and I'm not distracted by other tasks, it takes me one month per galaxy to reduce the VLA data."

The extensive data are poised to re-shape astronomers' understanding of star formation. "The crux of the problem is that the standard models for galaxies don't work for dwarfs. Dwarfs should not be forming stars at all."

But indeed they are. They are forming stars even at their outer edges. The little-understood portions of dwarf irregular galaxies are what intrigue Hunter most of all.

"It's the outer disks--because they are so extreme," she said. "These are such extreme environments that they are very stringent tests for star formation."

Clue to Mars' Past Environment for Life

Rocks examined by NASA's Spirit Mars Rover hold evidence of a wet, non-acidic ancient environment that may have been favorable for life. Confirming this mineral clue took four years of analysis by several scientists.

An outcrop that Spirit examined in late 2005 revealed high concentrations of carbonate, which originates in wet, near-neutral conditions, but dissolves in acid. The ancient water indicated by this find was not acidic.

NASA's rovers have found other evidence of formerly wet Martian environments. However the data for those environments indicate conditions that may have been acidic. In other cases, the conditions were definitely acidic, and therefore less favorable as habitats for life.

Laboratory tests helped confirm the carbonate identification. The findings were published online Thursday, June 3 by the journal Science.

"This is one of the most significant findings by the rovers," said Steve Squyres of Cornell University in Ithaca, N.Y. Squyres is principal investigator for the Mars twin rovers, Spirit and Opportunity, and a co-author of the new report. "A substantial carbonate deposit in a Mars outcrop tells us that conditions that could have been quite favorable for life were present at one time in that place. "

Spirit inspected rock outcrops, including one scientists called Comanche, along the rover's route from the top of Husband Hill to the vicinity of the Home Plate plateau which Spirit has studied since 2006. Magnesium iron carbonate makes up about one-fourth of the measured volume in Comanche. That is a tenfold higher concentration than any previously identified for carbonate in a Martian rock.

"We used detective work combining results from three spectrometers to lock this down," said Dick Morris, lead author of the report and a member of a rover science team at NASA's Johnson Space Center in Houston."The instruments gave us multiple, interlocking ways of confirming the magnesium iron carbonate, with a good handle on how much there is."

Massive carbonate deposits on Mars have been sought for years without much success. Numerous channels apparently carved by flows of liquid water on ancient Mars suggest the planet was formerly warmer, thanks to greenhouse warming from a thicker atmosphere than exists now. The ancient, dense Martian atmosphere was probably rich in carbon dioxide, because that gas makes up nearly all the modern, very thin atmosphere.

It is important to determine where most of the carbon dioxide went. Some theorize it departed to space. Others hypothesize that it left the atmosphere by the mixing of carbon dioxide with water under conditions that led to forming carbonate minerals. That possibility, plus finding small amounts of carbonate in meteorites that originated from Mars, led to expectations in the 1990s that carbonate would be abundant on Mars. However, mineral-mapping spectrometers on orbiters since then have found evidence of localized carbonate deposits in only one area, plus small amounts distributed globally in Martian dust.

Morris suspected iron-bearing carbonate at Comanche years ago from inspection of the rock with Spirit's Moessbauer Spectrometer, which provides information about iron-containing minerals. Confirming evidence from other instruments emerged slowly. The instrument with the best capability for detecting carbonates, the Miniature Thermal Emission Spectrometer, had its mirror contaminated with dust earlier in 2005, during a wind event that also cleaned Spirit's solar panels.

"It was like looking through dirty glasses," said Steve Ruff of Arizona State University in Tempe, Ariz., another co-author of the report. "We could tell there was something very different about Comanche compared with other outcrops we had seen, but we couldn't tell what it was until we developed a correction method to account for the dust on the mirror."

Spirit's Alpha Particle X-ray Spectrometer instrument detected a high concentration of light elements, a group including carbon and oxygen, that helped quantify the carbonate content.

The rovers landed on Mars in January 2004 for missions originally planned to last three months. Spirit has been out of communication since March 22 and is in a low-power hibernation status during Martian winter. Opportunity is making steady progress toward a large crater, Endeavour, which is about seven miles away.