Posted on by Fraser Cain

Selecting Stars Very Similar to Our Own

Image credit: John Rowe

The search for Earthlike planets begins with the search for Sunlike stars. At the top of the list is a reasonably nearby star called 37 Gem; located in the Gemini constellation. Astronomer Maggie Turnbull was asked to make a short list of thirty candidate stars that closely matched our own Sun out of a total list 2,350 stars which are within one hundred light years from us. This short list, including 37 Gem will be used by the Terrestrial Planet Finder mission, which will search for habitable planets by looking for the visible light of oxygen or water in an Earthlike planet – a sure sign of life.

The thirty-seventh most westerly star in the constellation, Gemini, is a yellow-orange star like our own sun. The star is called 37 Geminorum, but for astrophysicist Margaret Turnbull, the star is special because it offers a case study for considering what might qualify as a good candidate for harboring habitable planets.

In building her list of stars that might support planets with liquid water and oxygen, she has to exclude suns that are extreme: either too young or too old, that rotate too fast, or that are variable enough in brightness to cause climatic chaos on any nearby world.

At a distance of 56.3 light-years away, the star 37 Gem has yet to show tell-tale signs of having such planets, or any planets–but future NASA and European telescopes are looking to target stars just like 37 Gem since they might share some of the same properties that made our own solar system habitable. More than 100 extrasolar planets have been found so far using ground-based telescopes, and estimates for the total such planets in our galaxy may total in the billions of candidate worlds.

Working from the University of Arizona in Tucson, Maggie Turnbull was asked to make a short list of thirty star candidates that most closely resembled other suns capable of supporting the conditions for life to flourish. Starting her search among stars less than one hundred light-years away yielded about 2,350 stars to consider further.

Turnbull recently presented her results to a group of scientists from NASA’s space-telescope project, the Terrestrial Planet Finder (TPF), which will search for habitable planets by using visible light with the “signature” of water and/or oxygen from an Earth-type planet. After TPF’s scheduled launch around 2013, will follow the European Darwin project involving six space telescopes.

The stellar list was pared down from an even larger list (17,129 stars within 450 light-years, or 140 parsecs), which Turnbull and adviser Jill Tarter of the SETI Institute first published in Astrophysical Journal. The list became known as the Catalog of Nearby Habitable Stellar Systems (or HabCat ). Their article published in August, entitled “Target Selection for SETI: I. A Catalog of Nearby Habitable Stellar Systems,” expanded previous candidate lists by nearly ten-fold, or an order-of-magnitude.

To support complex life, a candidate star must be the right color, brightness, and age. If it is a middle-aged star like our own, it will have burned through enough fusionable light elements to produce heavier metals like iron, but not so old that it is collapsing or so young that life is only a distant future prospect. Based on what fragments we know about how complex life appeared on Earth, Turnbull’s search aims to find the ‘Goldilocks’ of stars that seems ‘just right’.

So why 37 Gem?
37 Geminorum lies in the northwest part of constellation Gemini , named after the Twins. For amateur astronomers with a good backyard telescope, 37 Gem is visible. In Greek mythology, the Gemini twins sailed with Jason in the quest for the Golden Fleece; during a storm, the twins helped save their ship ARGO from sinking, and so the constellation became much valued by sailors.

Most stars like Gem 37 are grouped into a small number of spectral classes, based roughly on the color of light they emit. Called the Henry Draper Catalog, the star compendium lists spectral classes in seven broad categories, from the hottest to the coolest stars. These types are designated, in order of decreasing temperature, by the letters O, B, A, F, G, K, and M. The nomenclature is rooted in long-obsolete ideas about stellar evolution, but the terminology remains. Our sun, classified on a finer scale as a typical ‘G2V’ dwarf, is approximately 4.5 billion years old. The candidate star, 37 Gem, is similarly middle-aged, but somewhat older by a billion years, at 5.5 billion years.

The spectra of G-type stars like our own (and 37 Gem) are dominated by certain chemical elements, as signaled by their characteristic spectral lines (or emissions). The elements of most current interest are metals, particularly for those star-signatures rich in iron, calcium, sodium, magnesium, and titanium. In astronomical terms, compared to our sun’s classification as a typical G2V dwarf, 37 Gem has a slightly hotter surface temperature. Thus Turnbull’s prime pick–37 Gem– is catalogued as a G0V dwarf–meaning it is also a yellow-orange main sequence dwarf star. Because G stars are characterized by the presence of these metallic lines and a weak hydrogen spectra, they share a common age, mass, and luminosity.

Otherwise, 37 Gem is close to our own solar twin, or a Gemini-like counterpart to the Sun: 1.1 times our sun’s mass, 1.03 times its diameter, and 1.25 times its luminosity.

Luminosities are “perhaps the most important information”, Turnbull told Astrobiology Magazine, “we use in determining the habitability of nearby stars” for complex life, because luminosity indicates which phase of life the star is in, and that in turn dictates how long the star will remain stable.

Astrobiology Magazine had the opportunity to talk with Maggie Turnbull at the Steward Observatory in Tucson about how to select stellar candidates for habitability.

Astrobiology Magazine (AM): Your recent survey began looking at around 100-light years distant from our Sun, and all stars inwards from that radius, correct? That was the visual sphere for starting the search?

Margaret Turnbull (MT): There are about 2,350 Hipparcos stars within 30 parsecs (90 light
years), the maximum distance for the Terrestrial Planet Finder (TPF) mission. There are about 5,000 total stars within that distance, but we are only looking at Hipparcos stars so my starting list is 2,350 stars long.

AM: Have you ever gotten hold of a backyard telescope to see 37 Gem?

MT: It should certainly be visible with a backyard telescope, but no, I haven’t looked at it with my own eyes! Because of the photometry (measuring its brightness) and spectroscopy (measuring its composition) I have looked at, I feel like I “know” it without ever having seen it.

However, there is more observing to be done for 37 Gem. For example, we do need to carry out high resolution infrared imaging of this star before we can say it should be a target–if we discover that there is a lot of debris floating around, we’ll have to take it off the list.

AM: Was the star, 37 Gem, much different from number two on the list of the thirty best candidates?

MT: Actually, the “best” stars are all very similar to one another, and in reality it doesn’t make much sense to try to rank them. 37 Gem happens to be one of the very nearest stars that also satisfies the engineering criteria, so at this time it looks like a very good candidate for the TPF search.

AM: Just out of curiousity, what star was officially number two on the list?

MT: When you are only going to look at thirty stars, they all better be “number one.” That is, every star we observe has to be of primary interest to the mission, because we have no time to waste. We are still in the process of precisely defining the primary mission goal.

If the goal is to look at range of spectral types, then the top stars may include very nearby K or M stars, but if the goal is to look at 30 of the most Sun-like stars, then stars like 18 Sco (a solar twin at 14 parsecs in the Constellation Scorpius), beta CVn (the “hound”), or 51 Peg (“Pegasus”, the flying horse) may end up being our best bets.

AM: Are there one or two pieces of missing data that would help the classification hone in better on star candidates?

MT: At this time, high-resolution infrared imaging is the missing piece of data that we definitely need. We need to know if these stars have dusty debris disks that would make it hard to detect planets orbiting there.

The Sun has a substantial amount of zodiacal dust because Jupiter is constantly stirring up the asteroid belt and as the asteroids collide they add dust to the Solar System.

A similar level of dust around other stars might not ruin our chances of seeing planets, but we’d certainly like to keep that to a minimum.

AM: What are your future plans for the stellar list in support of the Terrestrial Planet Finder and Darwin missions?

MT: I haven’t yet presented my ‘final’ list to the TPF science working group on Nov 18th and 19th at the US Naval Observatory, during a meeting with others who are creating their own lists.

I have already presented my methodology to the group, but now we will be meeting with engineers who will explain to us the constraints of the instrument and we will have to refine further the list to accommodate their criteria.

Their criteria will include things like: can’t have a companion star within several arcseconds even if the companion is not a concern for planet stability, because the extra light will contaminate the field of view; can’t look at stars fainter than about 6th magnitude; can only look at stars at least ~60 degrees away from the Sun during the whole year, etc.

AM: You published your first catalog of habitable stars in August of this year, and there is a part two to that classification. What are the main plans for Part II of the HabCat?

MT: Jill Tarter and I have recently submitted a second paper on the SETI target list which will appear in the Astrophysical Journal Supplements in December. This paper gives a list of old, high metallicity open clusters, the nearest 100 stars regardless of stellar type, and about 250,000 main sequence stars from the Tycho Catalogue, all of which will be observed by the Allen Telescope Array (ATA) whenever a HabCat star isn’t available for us to observe.

The primary ATA beam will be pointed by radio astronomers, and they will be making very high resolution maps of their own targets, while at the same time we will be observing HabCat stars (or stars from our lists in Paper 2) for SETI.

AM: Finally, are the missions, Kepler and TPF, planning the kinds of enhancements that would yield a detection of more Earth-sized planets, not just gas giants, for a given star in their surveys?

MT: Yes. Kepler will give us an indication of how common terrestrial planets are by watching thousands of sun-like stars for “transits”–events where the planet actually passes in front of the star it is orbiting and temporarily blocks a little of the star’s light.

Terrestrial Planet Finder will follow up on this by actually imaging planets orbiting the nearest stars, and telling us whether these planets have atmopheres by taking spectra.

We can look for water, oxygen, and carbon dioxide, and if we’re lucky we may even see some direct indications of life in the form of a vegetation signature or strong atmospheric disequilibrium, such as the simultaneous presence of oxygen and methane (due to the simultaneous presence of plants and methanogen bacteria on Earth).

What’s Next
Any mission to detect and spectroscopically characterize terrestrial planets around other stars must be designed so that it can detect diverse types of terrestrial planets with a useful outcome. Such missions are now under study–the Terrestrial Planet Finder (TPF), by NASA, and Darwin by ESA, the European Space Agency. The principal goal of TPF/Darwin is to provide data to the biologists and atmospheric chemists.

The TPF/Darwin concept hinges on the assumption that one can screen extrasolar planets for habitability spectroscopically. For such an assumption to be valid, we must answer the following questions. What makes a planet habitable and how can they be studied remotely? What are the diverse effects that biota might exert on the spectra of planetary atmospheres? What false positives might we expect? What are the evolutionary histories of atmospheres likely to be? And, especially, what are robust indicators of life?

TPF/Darwin must survey nearby stars for planetary systems that include terrestrial sized planets in their habitable zones (“Earth-like” planets). Through spectroscopy, TPF/Darwin must determine whether these planets have atmospheres and establish whether they are habitable.

The Kepler mission is also scheduled for launch into solar orbit in October 2006. Kepler is intended as a mission to determine the frequency of inner planets near the habitable zone of a wide range of stars. Kepler will simultaneously observe 100,000 stars in our galactic “neighborhood,” looking for Earth-sized or larger planets within the “habitable zone” around each star – the not-too-hot, not-too-cold zone where liquid water might exist on a planet.

To highlight the difficulty of detecting an Earth-sized planet orbiting a distant star, Kepler’s principal investigator, William Borucki of NASA Ames points out it would take 10,000 Earths to cover the Sun’s disk. One NASA estimate says Kepler should discover 50 terrestrial planets if most of those found are about Earth’s size, 185 planets if most are 30 percent larger than Earth and 640 if most are 2.2 times Earth’s size. In addition, Kepler is expected to find almost 900 giant planets close to their stars and about 30 giants orbiting at Jupiter-like distances from their parent stars.

Because most of the gas giant planets found so far orbit much closer to their stars than Jupiter does to the Sun, Borucki believes that during the four- to six-year mission, Kepler will find a large proportion of planets quite close to stars. If that proves true, he says, “We expect to find thousands of planets.”

Using present methods, astronomers today would find it very difficult to detect an Earth-sized planet around the star 37 Gem. Past analyses have however ruled out some choices. For instance, a giant planet like our own Jupiter or Saturn does not orbit around 37 Gem. These studies have suggested that giant planets of one-tenth to 10 times the mass of Jupiter do not exist close to 37 Gem (within 0.1 to four astronomical units, or one earth-sun distance, AUs, see also Cummings et al, 1999 ). Because of the challenges of finding dim planets near to much brighter stars, almost all of the extrasolar planets found so far are like our own Jupiter–massive, probably gaseous, and unlikely to harbor conditions for life owing to their close proximity to a parent star.

But conditions around 37 Gem might support smaller, inner planets like Venus or Earth. No one knows. Only future surveys will have the instrumentation capable of finding such Earth-like planets.

Models of stars like 37 Gem, do however, support the possible existence of at least one stable orbit for an Earth-like planet (with liquid water) centered around one earth-sun distance (1.12 AU). Such a presumed planet would orbit between the distances of Earth and Mars in our Solar System. This undiscovered planet, if it can be detected in future studies, would have a year that lasts more than 450 days, or an orbital period of around 1.3 Earth-years.

Since oxygen-generating life on Earth took about two billion years to take hold, stars much younger than this would likely not have had sufficient time for life to evolve towards any complex forms. Given the billions of years required for evolution of life on earth, scientists could question whether life would stand a chance in a shorter-lived solar system. Hotter, more massive stars have always been considered less likely to harbor life but not because they would be too hot. Planets could still enjoy temperate climates, just further out than Earth is from the Sun, and at orbits farther away from the its own parent star. The first problem of habitability is one of time, not temperature. Hotter stars tend to burn out faster — perhaps too fast for life to develop there.

Original Source: Astrobiology Magazine

Posted on by Fraser Cain

Spirit Reaches Out to Adirondack

Image credit: NASA/JPL

Spirit is reaching out to test the nearby rock, “Adirondack”, which controllers targeted to get a better understanding of its composition and origin; it will be performing a series of tests today and tonight. The rover already used its instruments to examine a patch of soil near the lander and found some surprising results: the soil in Gusev Crater seems volcanic in origin, not sedimentary. Its instruments have also found the presence of a mineral called olivine, which doesn’t resist weathering very well and is normally evidence of volcanic deposits.

The first use of the tools on the arm of NASA’s Mars Exploration Rover Spirit reveals puzzles about the soil it examined and raises anticipation about what the tool will find during its studies of a martian rock.

Today and overnight tonight, Spirit is using its microscope and two up-close spectrometers on a football-sized rock called Adirondack, said Jennifer Trosper, mission manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

“We’re really happy with the way the spacecraft continues to work for us,” Trosper said. The large amount of data — nearly 100 megabits — transmitted from Spirit in a single relay session through NASA’s Mars Odyssey spacecraft today “is like getting an upgrade to our Internet connection.”

Scientists today reported initial impressions from using Spirit’s alpha particle X-ray spectrometer, Moessbauer spectrometer and microscopic imager on a patch of soil that was directly in front of the rover after Spirit drove off its lander Jan. 15.

“We’re starting to put together a picture of what the soil at this particular place in Gusev Crater is like. There are some puzzles and there are surprises,” said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the suite of instruments on Spirit and on Spirit’s twin, Opportunity.

One unexpected finding was the Moessbauer spectrometer’s detection of a mineral called olivine, which does not survive weathering well. This spectrometer identifies different types of iron-containing minerals; scientists believe many of the minerals on Mars contain iron. “This soil contains a mixture of minerals, and each mineral has its own distinctive Moessbauer pattern, like a fingerprint,” said Dr. Goestar Klingelhoefer of Johannes Gutenberg University, Mainz, Germany, lead scientist for this instrument.

The lack of weathering suggested by the presence of olivine might be evidence that the soil particles are finely ground volcanic material, Squyres said. Another possible explanation is that the soil layer where the measurements were taken is extremely thin, and the olivine is actually in a rock under the soil.

Scientists were also surprised by how little the soil was disturbed when Spirit’s robotic arm pressed the Moessbauer spectrometer’s contact plate directly onto the patch being examined. Microscopic images from before and after that pressing showed almost no change. “I thought it would scrunch down the soil particles,” Squyres said. “Nothing collapsed. What is holding these grains together?”

Information from another instrument on the arm, an alpha particle X- ray spectrometer, may point to an answer. This instrument “measures X-ray radiation emitted by Mars samples, and from this data we can derive the elemental composition of martian soils and rocks,” said Dr. Johannes Brueckner, rover science team member from the Max Planck Institute for Chemistry, Mainz, Germany. The instrument found the most prevalent elements in the soil patch were silicon and iron. It also found significant levels of chlorine and sulfur, characteristic of soils at previous martian landing sites but unlike soil composition on Earth.

Squyres said, “There may be sulfates and chlorides binding the little particles together.” Those types of salts could be left behind by evaporating water, or could come from volcanic eruptions, he said. The soil may not have even originated anywhere near Spirit’s landing site, because Mars has dust storms that redistribute fine particles around the planet. The next target for use of the rover’s full set of instruments is a rock, which is more likely to have originated nearby.

Spirit landed in the Connecticut-sized Gusev Crater on Jan. 3 (EST and PST; Jan. 4 Universal Time). In coming weeks and months, according to plans, it will examine rocks and soil for clues about whether the past environment there was ever watery and possibly suitable to sustaining life. Spirit’s twin Mars Exploration Rover, Opportunity, will reach Mars on Jan. 25 (EST and Universal Time; 9:05 p.m., Jan. 24, PST) to begin a similar examination of a site on the opposite side of the planet.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C. Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu .

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Latest Status on the Shuttle’s Return to Flight

Image credit: NASA

It looks like NASA is still a long way from getting the space shuttles ready to fly again, according to the interim report released today by the Return to Flight task group. Although NASA is addressing all 29 issues suggested by the recommendations of the Columbia Accident Investigation Board, the progress is reported as “uneven”. So far, none of the tasks have been completed. NASA is currently targeting September 12 for the date of the first shuttle launch after the Columbia disaster, but many experts think that date could be pushed back even further.

The Stafford-Covey Return to Flight Task Group will issue an interim report Tuesday, Jan. 20. The group is making an independent assessment of NASA’s implementation of the Columbia Accident Investigation Board Space Shuttle return to flight recommendations.

http://returntoflight.org

Co-Chairman Richard Covey will be available to answer questions from the news media at 2:30 p.m. EST, Wednesday, Jan. 21 at the Task Group office at 1740 NASA Parkway, Suite 101, Houston. A telephone bridge will be provided for media unable to attend in person. Interested media should call Shannon Bach at: 281/792-7523 no later than 11 a.m. EST. Jan. 21.

The 28-member task group is co-chaired by Covey, a former Space Shuttle Commander and retired Air Force Lieutenant General and former Apollo Mission Commander Thomas Stafford. The Task Group will continue to report results to NASA at appropriate intervals and will provide a final report to the agency approximately one month before the Space Shuttle’s return to flight.

Original Source: RTF TG News Release

Posted on by Fraser Cain

Humans Will Need Robots to Go to Mars

Image credit: NASA

Before humans can take the first tentative steps onto the Martian surface, our robots will have spent many years examining the planet to let us know exactly what to expect. Spirit and Opportunity will examine the dirt to see if there’s water that can be extracted. They’ll also examine the dust to see if it contains chemicals that could be detrimental to humans if it was inhaled. Robots will also help us figure out the best location humans should go to maybe mine for subsurface reserves of water or stay protected from the solar radiation.

Around the same time when Spirit?s older sister, Sojourner, was testing rover technologies on Mars during the Pathfinder mission in 1997, Mars Exploration Rover soil scientist, Doug Ming, was ?living off the martian land,? locked away in a biosphere for 30 days, sacrificing his normal life on Earth to experience ?living? on Mars. ?We simulated how astronauts would work, eat, and conduct experiments on Mars, and we even had to recycle our own urine – create purified water from it – to survive the sparse water resources on Mars,? laughed Ming.

After 15 years of researching plant growth systems and irrigation techniques for humans to use both on the Moon and Mars, Doug Ming is currently utilizing the Spirit rover to further understand the nitty-gritty composition of the dirt on Mars. His analysis will help meet the mission goal of understanding whether Gusev Crater was ever a lake. In the long term, however, studies of soil characteristics will help future scientists develop ways to extract useful materials for their colonies and safely arrive and survive on the red planet.

Humans Need Oxygen, Water, and Shelter on Mars
?In NASA?s Advanced Life Support Program, we regenerate the air by using plants to convert carbon dioxide into oxygen in closed chambers. To live safely on Mars, which has 95% carbon dioxide in its atmosphere, we?ll have to create a lot of technology tricks like that to survive,? explained Ming. Explorers visiting Mars will have to live in habitats where the oxygen is regenerated, wear spacesuits with oxygen masks, drive radiation-proof vehicles, and grow food by adding nutrients to the ?topsoil? that currently seems unable to nourish plants. But before astronauts can do all of these activities on Mars, robots need to teach humans where and how to land, where to build, and how to survive in the harsh martian environment. ?The Mini-TES instrument on Spirit is searching for water bound in soils and rocks on Mars. Water bound up in the soil and rocks could be extracted by astronauts to use as nourishment for themselves or fuel for their machines,? said Ming.

Science instruments on Spirit’s robotic arm will provide information on the martian environment that may be helpful for future human explorers.

Dirt That Hurts
?We?re also studying the chemical composition of the soil on Mars with our M?ssbauer Spectrometer and APXS instruments, which will tell us what chemicals might be detrimental to humans if they inhale the dust. For example, trace metals could be toxic to lungs, and dust could also affect electronic devices like computers and vehicles that humans will need on Mars. We?re also concerned that dust and soil could have the potential to develop electric charges. We?re taking pictures and making ?mini-movies? of dust devils that will better help us understand dust and soil movement on Mars? said Ming.

Location, Location, Location
Where should humans land on Mars? Where does enough subsurface water ice exist that humans could drill and extract? Where does the radiation penetrate the surface the least to prevent sickness and cancer-causing exposure to humans? Where is the ground strong enough to withstand a heavy human-filled mini-apartment building with parking spots for martian cars and spaceships? How do you enter the martian atmosphere with a spaceship at least thirty times larger and heavier than any spaceship humans have ever sent to Mars?

Scientists and engineers must figure out the answers to these complicated questions through the knowledge they gain from the robots sent before humans. ?Engineers and navigators will study how hot the spacecraft heat shield got as it entered the martian atmosphere, which will help future engineers model, design, and build heat shields that will ultimately protect humans as they land on Mars,? explained Ming. The The Martian Radiation Environment Experiment on NASA?s Mars Odyssey orbiter already successfully calculated that the radiation exposure on the way to Mars is twice the amount of radiation exposure that humans encounter in low-Earth orbit. Scientists are currently taking that data to model what the radiation levels would be on the surface of Mars to help build protective materials for humans during the flight to Mars and living on Mars.

Robots Pave the Way for Humans
?First and foremost, the Mars Exploration Rover mission and every mission to Mars are scientifically exciting in the present because we instantly learn about our neighboring planet. By comparing Earth to Mars, we learn more about how to protect our home planet,? said Ming. But, everything we learn now will also help us grow and evolve as explorers at exponential levels for the future. ?Space navigators still incorporate sky charts drawn by Babylonian star gazers to send spacecraft on a perfect trajectory to Mars today. Humans going to Mars – soon or even thousands of years from now – will depend on what we learn from our current robotic missions to create the right spacesuits, habitats, and roving vehicles humans will someday drive on Mars,? said Ming. ?Robots will probably even deliver our first building materials to Mars, so when humans first land, robots will have paved the way for us in more ways than one,? said Ming.

Original Source: NASA News Release

Posted on by Fraser Cain

Photo Gallery: Mars Express First Image

Here’s a 1024×768 resolution wallpaper of the amazing first photograph of Mars taken by the European Space Agency’s Mars Express spacecraft. The stereoscopic image was taken on January 14, 2004 by Mars Express when it was 275 kilometres above the Valles Marineris – a 1700 km long by 65 km wide canyon that runs across the surface of Mars.

Posted on by Fraser Cain

Spirit Investigates a Nearby Rock

Image credit: NASA/JPL

NASA’s Mars Exploration Rover Spirit drove a few metres yesterday to get nice and close to a large rock nearby the landing site which scientists have dubbed “Adirondack”. Spirit will examine the rock with its microscope and two instruments that will reveal its composition. To make the drive to this rock, Spirit turned 40-degrees and then rolled 1.9 metres. Engineers are still taking “baby steps” with Spirit, since this first target took the rover 30 minutes to travel.

NASA’s Spirit rover has successfully driven to its first target on Mars, a football-sized rock that scientists have dubbed Adirondack.

The Mars Exploration Rover flight team at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., plans to send commands to Spirit early Tuesday to examine Adirondack with a microscope and two instruments that reveal the composition of rocks, said JPL’s Dr. Mark Adler, Spirit mission manager. The instruments are the M?ssbauer spectrometer and the alpha particle X-ray spectrometer.

Spirit successfully rolled off the lander and onto the martian surface last Thursday. To make the drive to Adirondack, the rover turned 40 degrees in short arcs totaling 95 centimeters (3.1 feet). It then turned in place to face the target rock and drove four short moves straightforward totaling 1.9 meters (6.2 feet). The moves covered a span of 30 minutes on Sunday, though most of that was sitting still and taking pictures between moves. The total amount of time when Spirit was actually moving was about two minutes.

“These are the sorts of baby steps we’re taking,” said JPL’s Dr. Eddie Tunstel, rover mobility engineer.

“The drive was designed for two purposes, one of which was to get to the rock,” Tunstel said. “From the mobility engineers’ standpoint, this drive was geared to testing out how we do drives on this new surface.” Gathering new information such as how much the wheels slip in the martian soil will give the team confidence for more ambitious drives in future weeks and months.

“Adirondack is now about one foot (30 centimeters) in front of the front wheels,” he said.

Scientists chose Adirondack to be Spirit’s first target rock rather than another rock, called Sashimi, that would have been a shorter, straight-ahead drive. Rocks are time capsules containing evidence of the environmental conditions of the past, said Dr. Dave Des Marais, a rover science-team member from NASA Ames Research Center, Moffett Field, Calif. “We needed to decide which of these time capsules to open.”

Sashimi appears dustier than Adirondack. The dust layer could obscure good observations of the rock’s surface, which may give information about chemical changes and other weathering from environmental conditions affecting the rock since its surface was fresh. Also, Sashimi is more pitted than Adirondack. That makes it a poorer candidate for the rover’s rock abrasion tool, which scrapes away a rock’s surface for a view of the interior evidence about environmental conditions when the rock first formed. Adirondack has a “nice, flat surface” well suited to trying out the rover’s tools on their first martian rock, Des Marais said.

“The hypothesis is that this is a volcanic rock, but we’ll test that hypothesis,” he said. Spirit arrived at Mars Jan. 3 (EST and PST; Jan. 4 Universal Time) after a seven-month journey. In coming weeks and months, according to plans, it will be exploring for clues in rocks and soil to decipher whether the past environment in Gusev Crater was ever watery and possibly suitable to sustain life.

Spirit’s twin Mars Exploration Rover, Opportunity, will reach Mars on Jan. 25 (EST and Universal Time; 9:05 p.m., Jan. 24, PST) to begin a similar examination of a site on the opposite side of the planet from Gusev Crater.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C. Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Stardust Surprised Scientists

Image credit: NASA/JPL

When NASA’s Stardust spacecraft swept past Comet Wild-2, it captured material from the comet’s tail and revealed incredible details about the surface of the fast moving object. The few images that Stardust was able to take also provided some surprises. Scientists anticipated that that comet would be a dusty snowball, with very few surface features, but Stardust found impact craters, barn-sized boulders, and tall cliffs. This indicates that the comet isn’t the loose collection of material that scientists theorized, since it’s obviously withstood quite a beating.

On Jan. 2nd, 2004, NASA’s Stardust spacecraft approached Comet Wild 2 and flew into a storm. Flurries of comet dust pelted the craft. At least half a dozen grains moving faster than bullets penetrated Stardust’s outermost defenses. The craft’s 16 rocket engines struggled to maintain course while a collector, about the size of a tennis racquet, caught some of the dust for return to Earth two years hence.

All that was expected.

Then came the surprise. It happened when Stardust passed by the core of the comet, only 236 km distant, and photographed it using a navigation camera. The images were intended primarily to keep the spacecraft on course. They also revealed a worldlet of startling beauty.

Right: The nucleus of Comet Wild 2 photographed by Stardust with approximately 20 meter resolution. Click on the image to see a much larger version.

At the heart of every comet lies a “dirty snowball,” a compact nucleus of dust and ice that the sun vaporizes, little by little, to form the comet’s spectacular tail. These nuclei are hard to see. For one thing, most are blacker than charcoal; they reflect precious little sunlight for cameras. Plus they’re hidden deep inside a cloud of vaporizing gas and dust, called “the coma.” Stardust’s plunge into Wild 2’s coma allowed it to view the nucleus at close range.

Previous flybys of Comet Halley by the European Giotto probe and Comet Borrelly by NASA?s Deep Space 1 revealed lumpy cores without much interesting terrain–as expected. These comets have been sun-warmed for many thousands of years. Solar heating has melted away their sharpest features.

Comet Wild 2, however, looks different. “We were amazed by the feature-rich surface of the comet,” says Donald Brownlee of the University of Washington, the mission’s principal investigator. “It is highly complex. There are barn-sized boulders, 100-meter high cliffs, and some weird terrain unlike anything we’ve ever seen before. There are also some circular features,” he adds, “that look like impact craters as large as 1 km across.”

“The high cliffs tell us that the crust of the comet is reasonably strong,” notes Brownlee. It’s probably a mixture of fine-grained rocky material held together by frozen water, carbon monoxide and methanol. Certainly a lander could touch down there, or an astronaut could walk across the surface without worrying too much about the ground collapsing.

An astronaut standing on Comet Wild 2 would see a truly fantastic landscape, speculates Brownlee. ?I imagine them inside one of the craters, surrounded by deep cliffs.” Icy spires, as tall as a person, might rise out of the crater floor. “These would be be the comet-equivalent of ‘snow spikes’ on Earth–those little jagged ridges that form when snow is exposed to sunlight and melts.”

Getting out of the crater would be easy. “Just jump,” says Brownlee, “but not too hard.” The comet?s gravity is only 0.0001-g, so “you could easily leap into orbit.”

Some of the photos from Stardust reveal gaseous jets. “The jets come from active regions on the comet’s surface, fissures or vents probably, where the ice is vaporizing and rushing into space,” Brownlee says. This is how mass is transferred from the comet’s nucleus to its tail.

Viewed from the surface, the jets would be nearly transparent. But an astronaut could spot them by looking for “dust entrained with the gas. Dust grains glinting in the sunlight would look like tracer bullets shooting out of the ground.”

A careful explorer could survey the entire 5-km nucleus in only a few hours, leaping high above the surface, dodging the occasional jet. “What an experience that would be,” he says.

There are billions of comets in the solar system. “We’ve gotten a close-up look at only three,” says Brownlee. And one of the three, Comet Halley, presented its night side to the cameras. So it’s too soon to say whether Comet Wild 2, among comets, is truly unusual.

Unlike comets Halley and Borrelly, notes Brownlee, “Wild 2 is a very recent arrival to the inner solar system.” For billions of years it orbited in the cold deep space beyond Jupiter, until 1974 when it was nudged by Jupiter’s gravity into a sun-approaching orbit. Since then the comet has passed by the Sun only five times; solar heating is only beginning to mold its surface.

And, according to Brownlee, that might be the key to the comet’s appearance. “Wild 2’s surface is a mixture of young and old that we haven’t see before,” he explains. Young features include possible sinkholes collapsing as the terrain is warmed. Impact craters and their ejecta, on the other hand, are old scars from time spent in the outer solar system.

The old parts of Wild 2 are what make the comet an attractive target for the Stardust probe, which captured a thousand or more grains of comet dust during the flyby. Such material, little altered since the formation of the solar system, could tell us a great deal about our origins.

The craft’s payload will return to Earth in 2006 for analysis by scientists. If a single picture from the navigation camera can surprise researchers, just imagine what’s in store when they get their hands on a thousand pieces of the comet itself.

Original Source: Science@NASA

Posted on by Fraser Cain

Planetary Nebula in Glowing Detail

Image credit: UA

Astronomers with the University of Arizona tested a new infrared camera on the 6.5-metre MMTO telescope, and produced an extremely detailed image of planetary nebula IC 2149. The object, located 3,600 light-years away, consists of a cloud of dust and gas shed from a dying star. The image is so clear because of the telescope’s adaptive optics system, which removes distortion caused by the Earth’s atmosphere – the telescope’s secondary mirror changes shape thousands of times a second to compensate for fluctuations in the light.

Astronomers testing a new near-infrared camera on southern Arizona’s 6.5-meter (21-foot) MMTO telescope have produced a sharp, detailed image of an aged planetary nebula basking in the light of its several-thousand-times brighter dying central star.

It is the most detailed wide-angle picture yet taken using the large telescope’s unique adaptive optics system, a technique that removes atmospheric blurring.

Astronomers from the University of Arizona’s Steward Observatory and Center for Astronomical Adaptive Optics made this picture of Planetary Nebula IC 2149 from exposures taken at the UA/Smithsonian MMT Observatory on 8,550-foot Mount Hopkins, Ariz. The planetary nebula, a cloud of gas and dust shed from a dying star, is 3,600 light-years away and 1.5 trillion miles (2.5 trillion kilometers) across.

The observers used UA astronomer Donald W. McCarthy’s near-infrared camera ARIES to search for specific gases in the star’s debris. They took images in three infrared colors of light, then combined them into a single false-color image.

While astronomers took the images, the large telescope’s secondary mirror changed its shape thousands of times each second to compensate in real-time for atmospheric turbulence that distorts starlight. The MMTO’s ultra-thin, 2-foot-diameter secondary mirror focuses light as steadily as if Earth had no atmosphere. For more about the MMTO’s superb adaptive optics, click here.

The resulting images demonstrate two benefits of the MMTO’s adaptive optics system, McCarthy and UA astronomy graduate student Patrick A. Young said.

First, the images are about three times sharper than images obtained with UA’s NICMOS cameras on the Hubble Space Telescope, and they are as sharp as Hubble images at shorter visible wavelengths.

Second, the sharper images show faint structure close to bright objects like stars in much greater detail. The image of IC2149 shows a contorted mixture of gas and dust several thousand times dimmer than the star itself. The halo around the star is the size of solar systems.

The team selected Planetary Nebula IC 2149 for the engineering tests of ARIES from 10 candidate targets during their telescope time last October, Young said.

“What you are seeing here is a star, a little less massive than the sun, that has used up all the fuel at its nuclear-burning core,” Young said. “Unable to produce energy, the core starts to contract, and turns into a ball of carbon and oxygen the size of the Earth. This gravitational contraction releases a lot of energy, and that causes the star to shed its outer atmosphere. The material we are actually seeing in the picture is the gas and dust being lit up by the light from the central star.”

Their observations suggest that all of the molecular hydrogen in the nebula has been destroyed by radiation from the central star, leaving only ionized hydrogen. Added to other evidence, this indicates that the nebula is several thousands of years old, Young said. Most planetary nebulae disperse and vanish in less than 10,000 years. The gas and dust ejected by the dying star contain heavy elements from which future planets may form.

Original Source: University of Arizona News Release

Posted on by Fraser Cain

First Image from Mars Express

Image credit: ESA

Even though it hasn’t reached its final operating orbit, the European Space Agency’s Mars Express has delivered some amazing images of the surface of Mars. This featured image shows a portion of the Martian Grand Canyon, called Valles Marineris, from two perspectives. It’s the first image to show the surface of Mars with such high resolution, in colour, and in 3D. Although it has so far failed to make contact with Beagle 2, the spacecraft will have several more opportunities when the lander goes into a special communications mode where it attempts to communicate constantly throughout the Martian day.

ESA’s Mars Express, successfully inserted into orbit around Mars on 25 December 2003, is about to reach its final operating orbit above the poles of the Red Planet. The scientific investigation has just started and the first results already look very promising, as this first close-up image shows.

Although the seven scientific instruments on board Mars Express are still undergoing a thorough calibration phase, they have already started collecting amazing results. The first high-resolution images and spectra of Mars have already been acquired.

This first spectacular stereoscopic colour picture was taken on 14 January 2004 by ESA?s Mars Express satellite from 275 km above the surface of Mars by the High Resolution Stereo Camera (HRSC). This image is available on the ESA Portal at: http://mars.esa.int

The picture shows a portion of a 1700 km long and 65 km wide swath which was taken in south-north direction across the Grand Canyon of Mars (Valles Marineris). It is the first image of this size that shows the surface of Mars in high resolution (12 metres per pixel), in colour, and in 3D. The total area of the image on the Martian surface (top left corner) corresponds to 120 000 km?. The lower part of the picture shows the same region in perspective view as if seen from a low-flying aircraft. This perspective view was generated on a computer from the original image data. One looks at a landscape which has been predominantly shaped by the erosional action of water. Millions of cubic kilometres of rock have been removed, and the surface features seen now such as mountain ranges, valleys, and mesas, have been formed.

The HRSC is just one of the instruments to have collected exciting data. To learn more about the very promising beginning to ESA’s scientific exploration of Mars, media representatives are invited to attend a press conference on Friday, 23 January 2004, at 11:00 CET at ESA?s Space Operations Centre in Darmstadt, Germany, and in video-conference with the other ESA centres.

There, under the auspices of ESA Council Chair, Germany’s Minister for Education and Research, Mrs Edelgard Bulmahn, ESA’s Director of the Scientific Programme, Prof. David Southwood and the Principal Investigators of all instruments on board Mars Express will present the first data and preliminary results.

Also a spectacular, three-dimensional video sequence, featuring famous landmarks on the surface of Mars ‘as seen through European eyes’ will be unveiled for the first time on Friday 23 January .

Original Source: ESA News Release

Posted on by Fraser Cain

Spirit Examines the Martian Soil

Image credit: NASA/JPL

NASA’s Spirit rover reached out and examined the Martian soil with its microscope instrument at the end of its robotic arm; this is the first microscopic image ever taken of another planet. The microscope can reveal objects as small as the width of a human hair, and will help scientists look at the fine details of rock to learn if they were formed by standing water. The rover will examine the same area with two other instruments: the M?ssbauer Spectrometer to find iron-bearing minerals, and the Alpha Particle X-ray Spectrometer which identifies the elements in rocks and soils.

NASA’s Spirit rover reached out with its versatile robotic arm early today and examined a patch of fine-grained martian soil with a microscope at the end of the arm.

“We made our first use of the arm and took the first microscopic image of the surface of another planet,” said Dr. Mark Adler, Spirit mission manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

The rover’s microscopic imager, one of four tools on a turret at the end of the arm, serves as the functional equivalent of a field geologist’s hand lens for examining structural details of rocks and soils.

“I’m elated and relieved at how well things are going. We got some great images in our first day of using the microscopic imager on Mars,” said Dr. Ken Herkenhoff of the U.S. Geological Survey Astrogeology Team, Flagstaff, Ariz. Herkenhoff is the lead scientist for the microscopic imagers on Spirit and on Spirit’s twin Mars Exploration Rover, Opportunity.

The microscope can show features as small as the width of a human hair. While analysis of today’s images from the instrument has barely begun, Herkenhoff said his first impression is that some of the tiny particles appear to be stuck together.

Before driving to a selected rock early next week, Spirit will rotate the turret of tools to use two spectrometer instruments this weekend on the same patch of soil examined by the microsope, said Jessica Collisson, mission flight director. The M?ssbauer Spectrometer identifies types of iron-bearing minerals. The Alpha Particle X-ray Spectrometer identifies the elements in rocks and soils.

The rover’s arm is about the same size as a human arm, with comparable shoulder, elbow and wrist joints. It is “one of the most dextrous and capable robotic devices ever flown in space,” said JPL’s Dr. Eric Baumgartner, lead engineer for the robotic arm, which also goes by the name “instrument deployment device.”

“Best of all,” Baumgartner said, “this robotic arm sits on a rover, and a rover is meant to rove. Spirit will take this arm and the tremendous science package along with it, and reach out to investigate the surface.”

The wheels Spirit travels on provide other ways to examine Mars’ soil. Details visible in images of the wheel tracks from the rover’s first drive onto the soil give information about the soil’s physical properties.

“Rover tracks are great,” said Dr. Rob Sullivan of Cornell University, Ithaca, N.Y., a member of the science team for Spirit and Opportunity. “For one thing, they mean we’re on the surface of Mars! We look at them for engineering reasons and for science reasons.” The first tracks show that the wheels did not sink too deep for driving and that the soil has very small particles that provide a finely detailed imprint of the wheels, he said.

Opportunity, equipped identically to Spirit, will arrive at Mars Jan. 25 (Universal Time and EST; 9:05 p.m. Jan. 24, PST). The amount of dust in the atmosphere over Opportunity’s planned landing site has been declining in recent days, said JPL’s Dr. Joy Crisp, project scientist for the Mars Exploration Rover Project.

Today, Spirit completes its 13th martian day, or “sol”, at its landing site in Gusev Crater. Each sol lasts 39 minutes and 35 seconds longer than an Earth day. The rover project’s goal is for Spirit and Opportunity to explore the areas around their landing sites for clues in the rocks and the soil about whether the past environments there were ever watery and possibly suitable for sustaining life.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover Project for NASA’s Office of Space Science, Washington, D.C. Pictures and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu.

Original Source: NASA/JPL News Release