New Clues Suggest Wet Era on Early Mars Was Global

PASADENA, Calif. -- Minerals in northern Mars craters seen by two orbiters suggest that a phase in Mars' early history with conditions favorable to life occurred globally, not just in the south.

Southern and northern Mars differ in many ways, so the extent to which they shared ancient environments has been open to question.

In recent years, the European Space Agency's Mars Express orbiter and NASA's Mars Reconnaissance Orbiter have found clay minerals that are signatures of a wet environment at thousands of sites in the southern highlands of Mars, where rocks on or near the surface are about four billion years old. Until this week, no sites with those minerals had been reported in the northern lowlands, where younger volcanic activity has buried the older surface more deeply.

French and American researchers report in the journal Science this week that some large craters penetrating younger, overlying rocks in the northern lowlands expose similar mineral clues to ancient wet conditions.

"We can now say that the planet was altered on a global scale by liquid water about four billion years ago," said John Carter of the University of Paris, the report's lead author.

Other types of evidence about liquid water in later epochs on Mars tend to point to shorter durations of wet conditions or water that was more acidic or salty.

The researchers used the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), an instrument on the Mars Reconnaissance Orbiter, to check 91 craters in the northern lowlands. In at least nine, they found clays and clay-like minerals called phyllosilicates, or other hydrated silicates that form in wet environments on the surface or underground.

Earlier observations with the OMEGA spectrometer on Mars Express had tentatively detected phyllosilicates in a few craters of the northern plains, but the deposits are small, and CRISM can make focused observations on smaller areas than OMEGA.

"We needed the better spatial resolution to confirm the identifications," Carter said. "The two instruments have different strengths, so there is a great advantage to using both."

CRISM Principal Investigator Scott Murchie of Johns Hopkins University Applied Physics Laboratory, Laurel, Md., a co-author of the new report, said that the findings aid interpretation of when the wet environments on ancient Mars existed relative to some other important steps in the planet's early history.

The prevailing theory for how the northern part of the planet came to have a much lower elevation than the southern highlands is that a giant object slammed obliquely into northern Mars, turning nearly half of the planet's surface into the solar system's largest impact crater. The new findings suggest that the formation of water-related minerals, and thus at least part of the wet period that may have been most favorable to life, occurred between that early giant impact and the later time when younger sediments formed an overlying mantle.

"That large impact would have eliminated any evidence for the surface environment in the north that preceded the impact," Murchie said. "It must have happened well before the end of the wet period."

Earth-like Planets May Be Ready for Their Close-Up

Many scientists speculate that our galaxy could be full of places like Pandora from the movie "Avatar" -- Earth-like worlds in solar systems besides our own.

That doesn't mean such worlds have been easy to find, however. Of the 400-plus planets so far discovered, none could support life as we know it on Earth.

"The problem with finding Earth-like planets," said Stefan Martin, an engineer at NASA's Jet Propulsion Laboratory, Pasadena, Calif., "is that their host stars can emit 10 million times more infrared light than the planet itself. And because planets like ours are small and orbit very close to their respective stars, it makes Earths almost impossible to see."

Together with A.J. Booth (formerly at JPL and now at Sigma Space Corp., Lanham, Md.), Martin may have developed a way to make this almost impossible feat a reality.

Their instrument design, called a "nulling interferometer," observes planets in infrared light, where they are easier to detect. It is designed to combine starlight captured by four different telescopes, arranging the light waves from the star in such a way that they cancel each other out. "We're able to make the star look dimmer -- basically turning it off," Martin said.

Nulling interferometry is not a new idea, but what sets the results from Martin and Booth apart is how effective it turned out to be. "Our null depth is 10 to 100 times better than previously achieved by other systems," Martin said. "This is the first time someone has cross-combined four telescopes, set up in pairs, and achieved such deep nulls. It's extreme starlight suppression."

That suppression could allow scientists to get a better look at exoplanets than ever before. "We're able to make the planet flash on and off so that we can detect it," Martin said. "And because this system makes the light from the star appear 100 million times fainter, we would be able to see the planet we're looking for quite clearly."

Pandora, up close and personal

Nulling interferometry isn't the only way scientists can find other Earths. NASA's Kepler mission, currently in orbit, is looking for Earth-like planets by watching the light of faraway stars dim slightly as their planets pass in front of them. Another method of observing exoplanets is coronagraphy, which uses a mask to block the optical light of a star, making its surrounding planets more easily visible. And the proposed SIM Lite mission would also be able to find nearby planets by observing the gravity-induced "wobbling" of their host stars.

However, Martin and Booth's nulling interferometer could eventually give astronomers the ability to get up close and personal with Earth-like worlds, analyzing their atmospheres for signs of habitability or even possibly life. "We expect to eventually be able to see hundreds of planets with this technique," Martin said.

The technology that they've developed could be used on a follow-up space mission to SIM Lite and Kepler. Martin is now planning to test the system in conditions that better mimic a real-life mission.

Once considered the stuff of science fiction, it may not be long before Earth-like planets, or, in the case of Pandora, Earth-like moons of giant planets, are found to exist other places besides the silver screen

Extreme Life on Earth Could Survive on Mars, Too

A new discovery of bacterial life in a Martian-like environment on Earth suggests our neighboring red planet could also be hospitable to some form of microbial life.
Researchers found methane-eating bacteria that appear to be thriving in a unique spring called Lost Hammer on Axel Heiberg Island in the extreme north of Canada.
This spring is similar to possible past or present springs on Mars, the scientists say, so it hints that microbial life could potentially exist there, too. There is no firm evidence that Mars does or ever did host life, however.
The Lost Hammer spring is extremely salty – so much so that the water doesn't freeze, even though temperatures are below freezing. The water has no consumable oxygen in it, but there are big bubbles of methane that rise to the surface.
And yet, the researchers found unique anaerobic organisms – creatures that don't need oxygen to survive – thriving in the spring. The hardy organisms most likely breathe sulfate instead of oxygen, the researchers said.
"The Lost Hammer spring is the most extreme subzero and salty environment we've found," said researcher Lyle Whyte, a microbiologist Canada's McGill University.
In fact, the temperatures in this part of Canada are even harsher than those found in many places on Mars.
"There are places on Mars where the temperature reaches relatively warm -10 to 0 degrees and perhaps even above 0ºC," Whyte said, "and on Axel Heiberg it gets down to -50, easy."
And recent data suggests Mars also has methane and frozen water.
"If you have a situation where you have very cold salty water, it could potentially support a microbial community, even in that extreme harsh environment."

Detailed Martian Scenes in New Images from Mars Orbiter

This image shows the west-facing side of an impact crater in the mid-latitudes of Mars' northern hemisphere. The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter took the image on April 13, 2010. It is one of 600 recent HiRISE observations newly released to NASA's Planetary Data System.

Like many mid-latitude Martian craters, this one has gullies along its walls that are composed of alcoves, channels and debris aprons. The origins of these gullies have been the subject of much debate; they could have been formed by flowing water, liquid carbon dioxide or dry granular flows. The orientation of these gullies is of interest because many craters contain gullies only on certain walls, such as those that are pole-facing. This could be due to changes in orbital conditions affecting long-term climate cycles and differences in solar heating along specific walls.

Many of the other features observed in and around this crater are indicative of an ice-rich terrain, which may lend credence to the water formation hypothesis for these gullies. The most notable of these features is "scalloped" terrain in and around the crater. This type of terrain has been interpreted as a sign of surface caving, perhaps due to sublimation of underlying ice. (Sublimation is the process of a solid changing directly to a gas.)

Another sign of ice is the presence of parallel lines and pitted material on the crater floor, similar to what is referred to as concentric crater fill. Parallel linear cracks are also observed along the crater wall over the gullies, which could be due to thermal contraction of ice-rich material.

All of these features taken together are evidence for ice-rich material having been deposited in this region during different climatic conditions, material that has subsequently begun to melt and/or sublimate under current conditions. More recently, wind-blown deposits have accumulated around the crater, as evidenced by the parallel ridges dominating the landscape. Dust devil streaks are also visible crossing the wind-sculpted ridges.

This image spans a distance of about 1.2 kilometers (three-fourths of a mile) and is presented in false color, which aids in distinguishing among surface materials and textures. It is a portion of the HiRISE observation catalogued as ESP_017405_2270, of an area centered at 46.7 degrees north latitude, 90.2 degrees east longitude. Other image products from this observation are available at http://hirise.lpl.arizona.edu/ESP_017405_2270.

NASA's Dawn Spacecraft Fires Past Record for Speed Change

PASADENA, Calif. - Deep in the heart of the asteroid belt, on its way to the first of the belt's two most massive inhabitants, NASA's ion-propelled Dawn spacecraft has eclipsed the record for velocity change produced by a spacecraft's engines.

The previous standard-bearer for velocity change, NASA's Deep Space 1, also impelled by ion propulsion, was the first interplanetary spacecraft to use this technology. The Deep Space 1 record fell on Saturday, June 5, when the Dawn spacecraft's accumulated acceleration over the mission exceeded 4.3 kilometers per second (9,600 miles per hour).

"We are using this amazing ion-engine technology as a stepping-stone to orbit and explore two of the asteroid belt's most mysterious objects, Vesta and Ceres," said Robert Mase, Dawn project manager from NASA's Jet Propulsion Laboratory in Pasadena, Calif.

A spacecraft's change in velocity refers to its ability to change its path through space by using its own rocket engines. This measurement of change begins only after the spacecraft exits the last stage of the launch vehicle that hurled it into space.

To get to where it is in both the record books and the asteroid belt, the Dawn spacecraft had to fire its three engines - one at a time-- for a cumulative total of 620 days. In that time, it has used less than 165 kilograms (363 pounds) of xenon propellant. Over the course of its eight-plus-year mission, Dawn's three ion engines are expected to accumulate 2,000 days of operation -- 5.5 years of thrusting -- for a total change in velocity of more than 38,620 kilometers per hour (24,000 miles per hour).

"I am delighted that it will be Dawn that surpasses DS1's record," said Marc Rayman, chief engineer for the Dawn mission and a previous project manager for Deep Space 1."It is a tribute to all those involved in the design and operations of this remarkable spacecraft."

At first glance, Dawn's pedal-to-the-metal performance is a not-so-inspiring 0-to-97 kilometers per hour (0-to-60 miles per hour) in four days. But due to its incredible efficiency, it expends only 37 ounces of xenon propellant during that time. Then take into consideration that after those four days of full-throttle thrusting, it will do another four days, and then another four. By the end of 12 days, the spacecraft will have increased its velocity by more than 290 kilometers per hour (180 miles per hour), with more days and weeks and months of continuous thrusting to come. In one year's time, Dawn's ion propulsion system can increase the spacecraft's speed by 8,850 kilometers per hour (5,500 miles per hour), while consuming the equivalent of only 16 gallons of fuel.

"This is a special moment for the spacecraft team," said Dawn's principal investigator, Chris Russell of the University of California Los Angeles. "In only 407 days, our minds will be on another set of records, the data records that Dawn will transmit when we enter Vesta orbit."

Dawn's 4.8-billion-kilometer (3-billion-mile) odyssey includes exploration of asteroid Vesta in 2011 and 2012, and the dwarf planet Ceres in 2015. These two icons of the asteroid belt have been witness to much of our solar system's history. By using the same set of instruments at two separate destinations, scientists can more accurately formulate comparisons and contrasts. Dawn's science instrument suite will measure shape, surface topography and tectonic history, elemental and mineral composition, as well as seek out water-bearing minerals. In addition, the way the Dawn spacecraft orbits both Vesta and Ceres will be used to measure the celestial bodies' masses and gravity fields.

While Dawn surpassed Deep Space 1's record for velocity change, Deep Space 1 will continue to reign as holder for the longest duration of powered spaceflight for another few months. Dawn is expected to take over that record on about August 10 of this year.

The Dawn mission to Vesta and Ceres is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate, Washington. The University of California, Los Angeles, is responsible for overall Dawn mission science. Other scientific partners include Planetary Science Institute, Tucson, Ariz.; Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany; DLR Institute for Planetary Research, Berlin, Germany; Italian National Institute for Astrophysics, Rome; and the Italian Space Agency, Rome. Orbital Sciences Corporation of Dulles, Va., designed and built the Dawn spacecraft.

View Back To Earth From Venus-bound Probe

What is Consuming Hydrogen and Acetylene on Titan?

PASADENA, Calif. - 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."