Universe Today

Image credit: NASA/JPL
Consistently highly rated among those memorable ‘money-shots’ from the current Mars’ surface exploration is a view looking back towards the Earth. On Thursday, the Spirit rover team released the banner image showing the Earth as a tiny gray dot in the martian sky near the horizon.

The history of such views backwards towards the home planet, Terra Firma, have captivated the imagination for a generation of astronomers. This glimpse from the surface of another planet offers an unrivalled perspective that stretches beyond just seeing our home as one of many planets, or the only pale blue dot in our solar system.

As Carl Sagan’s widow, Anne Druyan , described this perspective image to Astrobiology Magazine, such earth views make “us look at this tiny planet, at the pale blue dot, and to see it in its real context, in its actual circumstances, in its true tininess. I don’t know anyone who’s able to really see that one-pixel Earth and not feel like they want to protect the Earth; that we have much more in common with each other than we’re likely to have with anyone anywhere else.”

The evocative phrase describing the Earth as a ‘pale blue dot’ was coined by Carl Sagan after seeing our planet as a single pixel. The view was taken from the departing Voyager spacecraft. The entire earth could be encompassed as a flicker of light. The first image of Earth ever taken from another planet that actually shows our home as a planetary disk was captured by the Mars Orbital Camera on May 8th.

One question that might be answerable from such a world-view is could a scientist on Mars identify from such a perspective that the Earth harbored life. In 1993, a team of researchers inspired by Carl Sagan, used an Earth fly-by of the Galileo spacecraft on its way to Jupiter to catch a glimpse of how the Earth might appear from afar. For astrobiologists, Sagan’s results were surprising.

Rather than seeing the Earth as an obvious candidate for life, the Galileo pictures gave surprisingly few clues of the biological potential of our own planet.

From afar, how Galileo missed the obvious signs of terrestrial life as we would have expected to see them, was at first disconcerting to the scientific community, because future missions aim to observe more distant extrasolar planets and detect what would be visible in the spectra–the ‘pale blue dot’ scenario.

One answer may lie in the fact that the spacecraft made its observations while still quite close to the Earth.

“The spectrograph was designed to look at small areas of Jupiter, so the field of view of the spectrograph was quite small,” said Nick Woolf of Arizona, in earlier discussions with the Astrobiology Magazine.

“Also, since the surface brightness of Jupiter [the Gaileo’s intended visual target] is far less than the Earth, the spectrograph detectors saturated except when the spectrograph was pointed at the darkest area of Earth – a cloud-free section of sea,” Woolf noted. The cloud-free sea is considered very dark relative to the dominance of bright clouds in a global picture of Earth. Thus it should come as no surprise that Galileo was successful in only imaging a relatively dark and lifeless planet, mainly because its design was not intended to look at Earth, but to probe Jupiter instead.

A spectroscope that might detect infrared or visible light looking back on Earth or outwards to other planets might focus mainly on four gases that are found in Earth’s atmosphere and linked to life:

* Water vapor A baseline sign, indicating the presence of liquid water, a requirement of known life.
* Carbon dioxide Can be created by biological and non-biological processes. Because it is necessary for photosynthesis, it would indicate the possible presence of green plants.
* Methane Considered suggestive of life, it also can be made both by biological and non-biological processes.
* Molecular oxygen (O2) – or its proxy, ozone (O3). The most reliable indicator of the presence of life, but still not conclusive.

Unless molecular oxygen in the atmosphere is constantly replenished by photosynthesis, it is quickly consumed in chemical reactions, in the atmosphere, on land and in seawater. So the presence of a large amount of oxygen in an extrasolar planet’s atmosphere would be a sign that it might host an ecosystem like present-day Earth’s.

An additional oxygen-related biosignature is the possibility of detecting green plants that make oxygen. Chlorophyll reflects near-infrared light very strongly, a phenomenon known as the “red edge” because the light is just beyond the range of colors human eyes can see. (If humans could see the red edge, plants would look red instead of green.) Near-infrared cameras would have no trouble picking up this distinctive signal.

Not only are earth-views aesthetically interesting, while offering a chance to test remote sensing scenarios, the rovers more practically depend on a daily sky view to navigate. The rover design does not possess any intrinsic way of knowing its orientation as north or south for instance, because Mars doesn’t offer a strong magnetic field that might typically give a compass reading. So scientists point the rover’s mobile panoramic camera to do a sun sighting daily, which also provides today’s orientation. Navigating by stars on Mars is also possible although the rovers’ solar power arrays typically are put into electronic sleep-modes at night to conserve power.

Spirit imaged stars on March 11, 2004, after it awoke during the martian night for a communication session with NASA’s Mars Global Surveyor orbiter. This image is an eight-second exposure. Longer exposures were also taken. The images tested the capabilities of the rover for night-sky observations. Scientists will use the results to aid planning for possible future astronomical observations from Mars.

Original Source: NASA Astrobiology Magazine

Image credit: NASA/JPL
NASA’s Spirit has begun looking down into a crater it has been approaching for several weeks, providing a view of what’s below the surrounding surface.

Spirit has also been looking up, seeing stars and the first observation of Earth from the surface of another planet. Its twin, Opportunity, has shown scientists a “mother lode” of hematite now considered a target for close-up investigation.

“It’s been an extremely exciting and productive week for both of the rovers,” said Spirit Mission Manager Jennifer Trosper at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

Dr. Chris Leger, a rover driver at JPL, said, “The terrain has been getting trickier and trickier as we’ve gotten close to the crater. The slopes have been getting steeper and we have more rocks.” Spirit has now traveled a total of 335 meters (1,099 feet).

Spirit’s new position on the rim of the crater nicknamed “Bonneville” offers a vista in all directions, including the crater interior. The distance to the opposite rim is about the length of two football fields, nearly 10 times the diameter of Opportunity’s landing-site crater halfway around the planet from Spirit.

Initial images from Spirit’s navigation camera do not reveal any obvious layers in “Bonneville’s” inner wall, but they do show tantalizing clues of rock features high on the far side, science-team member Dr. Matt Golombek of JPL said at a news briefing today. “This place where we’ve just arrived has opened up, and it’s going to take us a few days to get our arms around it.?

Scientists anticipate soon learning more about the crater from Spirit’s higher-resolution panoramic camera and the miniature thermal emission spectrometer, both of which can identify minerals from a distance. They will use that information for deciding whether to send Spirit down into the crater.

From the crater rim and during martian nighttime earlier today, Spirit took pictures of stars, including a portion of the constellation Orion. Shortly before dawn four martian days earlier, it photographed Earth as a speck of light in the morning twilight. The tests of rover capabilities for astronomical observations will be used in planning possible studies of Mars’ atmospheric characteristics at night. Those studies might include estimating the amounts of dust and ice particles in the atmosphere from their effects on starlight, said Dr. Mark Lemmon, a science team member from Texas A&M University, College Station.

Opportunity has been looking up, too. It has photographed Mars’ larger moon, Phobos, passing in front of the Sun twice in the past week, and Mars’ smaller moon, Deimos, doing so once.

Opportunity’s miniature thermal emission spectrometer has taken upward-looking readings of the atmospheric temperature at the same time as a similar instrument, the thermal emission spectrometer on NASA’s Mars Global Surveyor orbiter, took downward-pointed readings while passing overhead. “They were actually looking directly along the same path,” said science team member Dr. Michael Wolff of the Martinez, Ga., branch of the Space Science Institute, Boulder, Colo. The combined readings give the first full temperature profile from the top of Mars’ atmosphere to the surface.?

When pointed at the ground, Opportunity’s miniature thermal emission spectrometer has checked the abundance of hematite in all directions from the rover’s location inside its landing-site crater. This mineral, in its coarse-grained form, usually forms in a wet environment. Detection of hematite from orbit was the prime factor in selection of the Meridiani Planum region for Opportunity’s landing site.

“The plains outside our crater are covered with hematite,” said Dr. Phil Christensen of Arizona State University, Tempe, lead scientist for the instrument. “The rock outcrop we’ve been studying has some hematite. Parts of the floor of the crater, interestingly enough, have virtually none.” The pattern fits a theory that the crater was dug by an impact that punched through a hematite-rich surface layer, he said. One goal for Opportunity’s future work is to learn more about that surface layer to get more clues about the wet past environment indicated by sulfate minerals identified last week in the crater’s outcrop.

Christensen said that before Opportunity drives out of the crater in about 10 days, scientists plan to investigate one area on the inner slope of the crater that he called “the mother lode of hematite.”

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 at http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Image credit: NASA/JPL
Since their arrivals on Mars, our two robotic wanderers have sent us incredible images and data from one of our nearest neighbors in the Solar System. The primary science objective of the Mars Exploration Rovers (MERs) is to determine to what degree the past action of liquid water on Mars has influenced the Red Planet’s environment over time.

While there is no direct evidence of liquid water on the surface of Mars today, the record of past water activity on Mars can be found in the rocks, minerals, and geologic landforms, particularly in some specific, diagnostic features that we believe form only in the presence of water. That is why both MERs are equipped with special tools to enable them to study a diverse collection of rocks and soils that may hold clues to past water activity on Mars and determine whether the planet ever had the potential to harbor life in the long-distant past, or, much less likely, today.

The information that NASA has gleaned in just the short amount of time that Spirit and Opportunity have been on the surface of Mars has been incredibly revealing. We have images that show rocks and surface structures in unprecedented detail. We are seeing a side of Mars that is vastly different from what we have encountered during past missions, because we targeted these special rovers to explore places that we knew would be compelling.

While we are incredibly pleased with the data and images we have obtained thus far and look forward to many more, we must not forget that traveling to and exploring Mars is a very challenging endeavor. As I have said many times before – both here on Capitol Hill and in the press – Mars is an extremely exciting and compelling Solar System destination, but it is also an incredibly difficult target, as history has often proven.

The landing and subsequent rollout of the two Rovers were practically picture perfect, which is a daunting engineering feat in and of itself, and one which makes me proud of NASA’s talented and capable Mars team. However, lest we became too confident about our Mars conquest, we were reminded of the significant challenges that operating on the Red Planet entails when the Spirit rover presented the Mars team with a serious technical challenge.

Spirit touched down in an area of Mars known as the Gusev Crater on January 4, 2004. After eighteen days of nearly flawless operation and after returning significant scientific data, including striking pictures of distant hills – and a rock affectionately dubbed “Adirondack ” – the Spirit rover developed an apparent communications problem that initially baffled the entire Mars team. In the ensuing days, Spirit sent us intermittent signals, and we sent the spacecraft numerous queries to try to diagnose the exact nature of the problem.

We were able to determine that the problem was related to software, and the team at JPL developed the necessary procedures and protocols to get Spirit back in business. Had Spirit’s communication problem been a hardware issue, we would be in much more dire straits for obvious reasons. Spirit is now performing as it was intended and continuing to explore its Martian surroundings.

Having actual data transmissions from Spirit’s descent to the Martian surface also provided significant benefits for the team planning the landing of the second Mars rover, Opportunity. Actual descent data from the first spacecraft were used to confirm our models of the behavior of the Martian atmosphere and weather – models which we depended on to plan Opportunity’s descent. The data from Spirit indicated that, while the descent was within the predicted limits of our engineering model, it was close to edge of the anticipated margins.

Armed with this new knowledge, NASA opted to open Opportunity’s parachute earlier to provide for a slower descent and a more gentle arrival on the Red Planet. On January 25, 2004, Opportunity bounced onto the opposite side of Mars – in an area called Meridiani Planum – from where its twin had landed.

The new landing location was “a world away ” from Gusev Crater in more ways than just distance. The initial images transmitted later that day fascinated the science team, revealing an area of dark soil and possible bedrock – a feature we have long searched for but never seen before on any planet’s surface – interspersed with patches of the more familiar red Martian soil. This region of Mars particularly interested planetary geologists because they believed it may contain abundant deposits of hematite, a mineral that, when found on Earth, has usually formed in the presence of persistent liquid water. We now know that their suspicions were correct.

On March 2, 2004, NASA announced that the Opportunity rover had found strong evidence that the area called Meridiani Planum was once soaking wet. Evidence found in an outcrop of rock led scientists to this important conclusion. Clues from the rocks’ composition, such as the presence of sulfates and salts, and the rocks’ physical attributes (e.g., niches where crystals once grew) helped make the case for a watery history. This area is scientifically compelling, and we intend to study it in further detail, hopefully revealing more secrets of the Red Planet.

Missions to Mars are launched approximately every two years (26 months), when the orbital alignments of the Earth and Mars allow the minimum amount of fuel to be used on the long trip. At each of these launch opportunities, NASA plans to send robotic spacecraft to Mars to continue searching for evidence of water, studying the rocks and soil of the planet, and attempting to answer the question, “Did life ever arise on Mars?” The Mars Exploration Program will attack this question by seeking to understand, in a systematic way, the current state and evolution of the atmosphere, surface, and interior of Mars, the potential for life on Mars in the past or present, and develop knowledge and technology necessary for future human exploration.

NASA’s Mars Program
This program is the result of an intensive planning process involving the broad science and technology community. The program incorporates the lessons learned from previous missions and builds upon, as well as responds to, scientific discoveries from past and on-going missions. In addition to the MERs, missions that comprise this systematic approach to Mars exploration are:

1. Mars Global Surveyor (MGS) – launched in 1996, this mission continues to return an unprecedented amount of data regarding Mars’ surface features and composition, atmosphere, weather, and magnetic properties. Scientists are using the data gathered from this mission both to learn about the Earth by comparing it to Mars and to build a comprehensive data set to aid in planning future missions. MGS also serves as a telecommunications relay for the MER missions, as well as a device for photographing landed spacecraft on the surface, such as the rovers.

2. Mars Odyssey – launched in 2001, the Odyssey orbiter is presently mapping the mineralogy and morphology of the Martian surface while achieving global mapping of the elemental composition of the surface and the abundance of hydrogen in the shallow subsurface. Its maps of hydrogen have suggested vast amounts of near-surface water ice in the polar regions of the planet. It also serves as a telecommunications relay for the MER missions.

3. Mars Reconnaissance Orbiter (MRO) – scheduled for launch in 2005, MRO will focus on analyzing the surface at unprecedented new scales in an effort to follow tantalizing hints of water detected in images from the MGS and Odyssey spacecraft and to bridge the gap between surface observations and measurements from orbit. For example, MRO will measure thousands of Martian landscapes at 20- to 30-centimeter (8- to 12-inch) resolution, enabling observation of features the size of beach balls, while also mapping their mineralogies. This will help NASA target future landed laboratories to the best sites to search for evidence of life.

4. Phoenix – scheduled to launch in 2007, this mission will conduct a stationary, surface-based investigation of water ice contained within Martian soils, as well as searching for organic molecules and observing modern climate dynamics. It aims to “follow the water” and measure indicator molecules at high-latitude sites where Mars Odyssey has discovered evidence of large water ice concentrations in the Martian soil. Phoenix was selected as the first of the competed Mars Scout missions.

5. Mars Science Laboratory (MSL) – schedule to launch in 2009, this next generation rover represents a major leap in surface measurements and pave the way for future sample return and astrobiology missions. A long-life power source is planned to allow the science laboratory to conduct experiments for up to two years. Instruments for this surface laboratory may provide direct evidence of organic materials, if any exist, and will be able to search up to several feet beneath the surface. MSL will also demonstrate technologies for accurate landing and hazard avoidance in order to reach what may be very promising, but difficult-to-reach, scientific sites. Its landing location will be based on observations by the Mars Reconnaissance Orbiter. In the ensuing decade, from 2011-2018, NASA plans additional science orbiters, rovers, and landers, and the first mission to return the most promising Martian samples to Earth.

Current strategies call for the first sample return mission to be launched by 2014. Options that would significantly increase the rate of missions launched and/or accelerate the schedule of exploration are under study. Technology development for advanced capabilities, such as miniaturized surface science instruments and deep drilling to several hundred feet, will also be carried out in this period.

NASA has developed a campaign to explore Mars that will change and adapt over time in response to what is discovered and learned with each mission. The plan is meant to be a robust, flexible, long-term program that will provide the highest probability for success. We are moving from the early era of global mapping and limited surface exploration to a much more intensive and discovery-responsive approach. We will establish a sustained presence in orbit around Mars and on the surface with long-duration exploration of some of the most scientifically promising and intriguing places on the planet.

We plan to “follow the water,” so that in the not-too-distant future we may finally know the answers to the most far-reaching questions about the Red Planet we humans have asked over the generations: Did life ever arise there, and does life exist there now?

What’s Next
On January 14, 2003, President Bush announced his new vision for NASA and the Nation’s space program, and just last month the President’s FY 2005 budget was released. Both of those events support and indeed strengthen NASA’s vision for Mars exploration over the next decade and beyond. NASA’s comprehensive, robotic approach to exploring Mars and learning the intricacies of its environment will not only seek to achieve the science goals outlined in this testimony, it will also serve as a solid foundation for the President’s vision of eventually conducting a human exploration mission to Mars.

Original Source: Astrobiology Magazine