.
One region of Mars has been picked by the Hungarian team as a "test field" for the dark dune spots, with sets of Mars Global Surveyor pictures of the selected landscape analyzed. That study area is a rectilinear ridged landform known as "Inca City", an informal name ascribed to the terrain from Mariner 9 images taken in the early 1970s.
Using the MGS pictures, the shape, pattern changes, fading and reappearance of the spots were catalogued. The Hungarian Mars analysts contend that the changes support a biological link to the alternations over a geological interpretation.
Constellation of patches
Team member, Eors Szathmary, a permanent fellow at the Institute for Advanced Study in Budapest, Hungary told SPACE.com that the Mars biology viewpoints are to be presented in several papers at the upcoming 33rd Lunar and Planetary Science Conference. That meeting is to be held by the Lunar and Planetary Institute this coming March in Houston, Texas.
Their assessments utilize MGS photos clicked from 1999 to 2001, from winter to summer of the southern hemisphere. Also used to help probe the dark dune area was information gleaned by a laser-scanning device toted by the MGS. That instrument yielded height information about the terrain, helping to discern various Sun illuminations that strike the area over periods of time.
Szathmary and his colleagues observed seasonal changes -- from early spring till early summer -- of the dark dune spots on frosted and defrosted
.
Each spring, they report, "gray fuzzy spots" appear in the bottom of the ice cover. By the middle of the first half of spring, these spots become darker, are bounded, and grow in size. By early summer defrosting, the naked dark soil of the dune is visible, and surrounded by a lighter ring.
Year by year, the dark dune spots "renew" on the same place with almost the same configuration, or "constellation" of patches. This repeat action, the team asserts, strengthens their suggestion of fixed, biological causes of spot formation.
Szathmary and others on the study group believe biology is at work on Mars.
"We interpret the sequence of dark dune spot formation and changes as a result of�probable Martian surface organisms," they report. The Martian organisms "survive below the surface ice, sunlight heats them up and they generate their living conditions."
Premature interpretation?
The Hungarian researchers concede, however, that other Mars researchers don't share a biological interpretation of the spots.
That's the case for Bruce Jakosky, a Mars researcher at the University of Colorado in Boulder. He also heads the university's Center for Astrobiology.
"Given our understanding of Mars volatile- and dust-related processes, it seems premature to attribute the characteristics that they identify to biological activity when other, simpler processes have not been ruled out," Jakosky told SPACE.com.
"In evaluating competing hypotheses, it is important to ask which is the most plausible by virtue of relying on well-understood processes that are likely to be occurring on Mars. It would be inadequate, for example, to treat all hypotheses that have not yet been absolutely ruled out as being of equal likelihood," Jakosky said.
Mars experts Mike Malin and Ken Edgett of Malin Space Science Systems in San Diego, California have also eyed the features. They report that straightforward defrosting of the Martian ice cover is responsible for the origin and development of the spots.
But the Hungarian team counters this view. After studying several thousand such spots, defrosting processes cannot be the sole explanation for the splotches in question, they say.
More information needed
Taking a measured, but too-early-to-tell attitude about the features is James Garvin, Mars Exploration Program Scientist at NASA Headquarters in Washington, D.C.
Garvin said that there are many physically plausible ways to generate the features that the Hungarian researchers are studying. Many of those ways are associated with the thermodynamics of materials at places on Mars where detailed measurements of the associated micro-environments are lacking.
"The dark spots on the polar dunes that are discussed deserve more attention, due to their intriguing time-variable behavior," Garvin said. "But we have to recognize that we are examining features at scales no finer than 10-20 feet, certainly not adequate to draw definitive conclusions about whether biological processes were involved in their origin," he said.
"To fully appreciate what is going on, it's imperative that we continue measurements of such localities with orbital and surface-based systems," Garvin said. Those include the Mars Reconnaissance Orbiter, as well as Scout landers and perhaps the Mars Smart Lander, he said.
The Hungarian team offers an interesting appraisal of what's causing the dark dune spots, said Ronald Greeley, a leading planetary geologist at Arizona State University in Tempe.
"Certainly the discovery of these features in the images rank with the most intriguing features revealed by Mars Global Surveyor's high-resolution camera. The Hungarians work through a set of logical descriptions and analyses of how the features might form, then draw the conclusion that dark dune spots are indicative of biological activity. Unfortunately, this last step is not convincing. It is not that this hypothesis is not possible, it is just that the data do not support it," Greeley said.
"No doubt, [this research] will generate much discussion, as is true for any suggestion of extraterrestrial life made by qualified planetary scientists. What the ensuing discussion will point to is the need for definitive (or at least reasonable) criteria for the detection of life, either with available instruments/data, or as a means to define new instruments," Greeley said.
Martian communities
Sizes of the various dark dune spots vary, and can be dozens of miles across. Their thickness varies from some 30 feet (10 meters) to over 650 feet (200 meters) on average.
"The shape, location, development and other features of the dark dune spots prompt us to suggest that some fluid phase must be involved in their explanation, which under the given circumstances cannot be anything else but liquid water. Dark dune spots are circular on flat surfaces. Defrosting cannot be responsible for this since it is affected by various surface conditions," one of the team's research paper's points out.
"We think that necessary melting of the ice is influenced by some biological factors," the researchers suggest. They propose one scenario, supporting their view that organisms are alive and well and at work on Mars.
If the Martian surface organisms do exist, they could dwell below the surface ice, the study team believes. When that ice is heated up by the organisms absorbing sunlight, they then grow and reproduce through photosynthesis. In this process, they generate their own living conditions.
"Not only liquid water, but even water vapor can sustain this form of life. Water vapor can migrate in the soil below the carbon dioxide frost cover supporting the living conditions for endolithic type communities and this activity enhances the defrosting/melting process on the top of the dark dune surface," the team concludes.
