DENVER, COLORADO - In many ways, you can get to Mars without stuffing yourself into a spacecraft.

Earth's big backyard is full of deserts, glaciers, acid pools, and volcanoes that offer tantalizing clues as to the red planet's past and present.

Researchers are trudging to far-flung and desolate spots on Earth, attempting to discern more about Mars. However, drawing out the truth about that distant world from Earth analogs can be tricky.

For one, Mars comes replete with less gravity than Earth. Then there's the lower atmospheric pressure. It's a cold, dry place to boot. In many places, layers of dust disguise the true face of Mars.

Scientists meeting here this week at the Geological Society of America's annual meeting discussed how best to scout about on our own terra firma to better understand Mars.

Head feels that a few million years is an "insignificant portion" of the almost 3 billion year long Amazonian period on Mars - the youngest subdivision of time on that planet. Where are the missing polar deposits, he asked, from the vast majority of the Amazonian period?

A huge cache of water ice once existed at Arsia Mons, Head speculates. High-resolution pictures of the area, as well as laser scan data of the terrain, both relayed from the Mars Global Surveyor, support the idea that ancient ice may still exist there. This working hypothesis builds upon earlier work of Mars researchers David H. Scott and James Zimbelman, he acknowledged.

By trekking down to Antarctica, Head hopes to find analogs to support the prospect that the deposit seen on Mars is perhaps the remnant of a mountain glacier.

Amazonian ice trapped below the surface at Arsia Mons, Head concluded, make it an ideal target for future exploration. "It's an exciting, potential possibility," he said.

Other researchers at the Geological Society of America's meeting point to a range of other Earth analogs, such as volcanoes and lava tubes, in order to better understand geological features on Mars.

But straightforward, one-to-one geological matches between worlds are not easily had.

Thanks to the steady stream of new Mars data pouring in from spacecraft, red planet re-looks are clearly justified, said volcano expert, NASA's Susan Sakimoto of the Goddard Space Flight Center. On the other hand, even the physics of terrestrial volcanism is not yet well understood, she cautioned.

Volcanic processes on Earth and those of Mars are "more complicated than meets the eye," said Scott Hughes from Idaho State University in Pocatello.

Larry Crumpler of the New Mexico Museum of Natural History sees merit in analyzing lava flows on Earth to better address features seen on Mars. Conversely, looking at Martian lava flows can yield clues as to how tongues of lava operate on our planet, he said.

Crumpler said that future robotic looks at surface rocks on Mars could help unravel whether the red planet had a higher or lower atmospheric pressure in the past.

Looking at extremely acid saline lakes and groundwater on Earth, like those found in Australia, may be good models for possible Martian environments. In fact, sulfuric acid flows could have carved out some landforms on Mars.

That's the view of researchers, Kathleen Benison and Deidre LaClair of Central Michigan University in Mt. Pleasant. They see chemical links between terrestrial acid deposits and minerals found on Mars. They report that many of the same sedimentary features and landforms found on Mars are also seen on a smaller scale in and near acid saline environments here on Earth.

Contrasting features viewed on Earth and Mars is a valid approach in gaining wisdom regarding both worlds, said Ted Maxwell, Associate Director for collections and research at the Smithsonian's National Air and Space Museum.

"The techniques that we use to explore both planets are going to valid for both places," Maxwell told SPACE.com. Part of that learning includes deciphering what happens to processes in reduced gravity and under reduced atmospheric pressure, like those found on Mars, he said.

Red planet research can be a two-way street.

In some cases, Maxwell said, intensive looks at dune formation and certain types of volcanoes on Mars has spurred more rigorous reviews of comparable features on Earth.

Maxwell said piecing together the climate history of Mars remains a tough assignment. Pulling the climate signature out of the red planet by studying its geology would be a real coup, he said.

"Did the climate on Mars change once, or shift back and forth? Are we looking back 3 billion years ago300 million years agoor 3,000 years ago for that climate change? And how often did it change subsequent to that?," Maxwell wonders.

Maxwell and colleague John Grant of the National Air and Space Museum's Center for Earth and Planetary Studies, support use of orbital and ground-penetrating radar to understand climate change on Earth, as well peel back the history of Mars.

For instance, space shuttle-carried radar has been used to reveal details of subsurface channels in southern Egypt - networks of buried "radar rivers", as Maxwell called them.

"If we had a similar technique to look through the sand on Mars and see what goes on underneathit would be a very different Mars," Maxwell said.

Europe's Mars Express that sets off for the red planet next year, as well as NASA's Mars Reconnaissance Orbiter in 2005, both carry gear that can carry out subsurface probing of the planet.

Grant called for the use of a specialized radar system in orbit around Mars. "This is the next logical step," he said.

Mars is mantled in many areas by a thick coat of dust, the origin of which is uncertain in many cases, Grant said. By orbiting Mars with powerful synthetic aperture radar hardware, the planet's dusty cover could be penetrated. More detail about subsurface ice pockets would be realized, as well as surface roughness and rock size distribution on Mars' topside, he said.

"As we've seen from the Mars Exploration Rover (MER) site selection process, understanding rock size distribution on the surface is absolutely essential to picking a safe landing site," Grant said.

Grant also called for consideration of ground penetrating radar equipment to be toted to Mars' surface aboard the 2009 Mars Smart Lander/Mobile Science Laboratory. "It's an ideal instrument" for that mission, he said, and is capable of a variety of on-the-spot jobs. Not only could that radar detect local shallow water, it could also help target drilling rigs to precisely reach such a valuable resource.

"You've only got one shot, probably. So you want to know where to put that drill down. With ground penetrating radar, it'll do the job," Grant concluded.