So what does Mars offer the senses?

This generation of Mars' rovers is delivering stunning images, in some cases at resolutions that zoom beyond the capacity of actually being there. The ability to see a panorama may be comparable to seeing it with your own eyes, particularly when the landscape is visualized using stereo pairs to obtain a three-dimensional picture.

'Seeing' Mars today offers the most lucid experience among the five senses, but even imagery is not without its caveats.

Even simple things, like the color of the sky, can be elusively difficult to pin down, as illustrated by an anecdotal challenge faced by the 1977 Viking team.

When scientists predicted that the Martian atmosphere might just be thick and dusty enough to scatter blue skylight, they assumed a calibration color in their initial photographs that made this 'blue-sky' presupposition correct. Only later in the mission, when better calibration was available, could a truer representation be provided.

According to Mars Global Surveyor image team member, Bill Hartmann, who described what happened during the difficult sky-color calibration on the Viking mission: "That amusing mistake with the first Viking 1 pictures -- releasing an image with a blue sky -- really was an example of what we didn't know and why we went there and what we were learning!" Even the color of the martian sky may play tricks on the imagination, when it comes to completing the sensory experience of another planet.

For a scientist, looking at true colors on Mars may mean a more precise thing than imagined by a casual martian tourist. Astronomy Professor, Woody Sullivan, from the University of Washington discussed how a color calibration target is needed to get a better picture. "By 'true colors', what does one mean by true? Do you mean what you would see on Mars? Or the scientific plot of intensity vs. wavelength?

The scattered light from various molecules and dust particles influence the colors that you would see. Not as it would appear in a vacuum. It has a blue or gray cast on Earth because of scattering. Even the Earth shadows are not black, but more bluish. So first, you need to correct for scattering on Mars. Ultimately you want to find what kinds of rocks are on Mars, so you want to see their colors as they would appear in a laboratory."

Using color calibration targets, noted Sullivan, "you look at those color scales on the Earth, as we calibrated their known values before launch, and then adjust the picture hue and tint to compensate for the local martian atmosphere or weather. The point is after taking the science data, of intensity vs. wavelength, a skilled person could translate that to what a human eye could see."

In addition to getting a good color match to the sky, it can be equally difficult to judge the ground hues as well. As Mars videographer, Dan Maas told Astrobiology Magazine, "Overall I think the weakest part of the [rover] animation is the Mars' surface terrain.

It doesn't quite capture the intricate details of the Martian rocks and soil. One day I hope to improve my terrain model so that I can render images that look just like panoramas from Pathfinder or MER." A visual walk around Mars can be further limited by the few places that cameras have so far mapped in high resolution.

'Hearing' Mars is another matter.
Earlier failed Mars missions --like the 1998 Mars Polar Lander--had ambitious plans for listening to the faint whistle of martian wind. The audio project was called the Mars Microphone, a project with unique opportunities to broadcast sound recordings globally on today's internet.

While the atmosphere on the surface of Mars is very thin, amounting to less than 1% of the pressure on Earth, laboratory experiments and theoretical calculations show that it is possible that sounds on Mars could be detected by standard microphone technology.

In the awkward situation of unprotected life-support in the open martian air, this thin atmosphere would not only decrease the sound intensity but also change the pitch and broadcast distances if two astronauts tried to yell across the martian plains. A more likely situation is the slow whistle of wind, as simulated by the Mars Exploration Rover video by Dan Maas.

One chance to listen on Mars is looming. In 2007 the French NetLander mission is scheduled to deploy a network of 4 identical landers to study the atmosphere and interior structure of Mars. Onboard each NetLander craft will be upgraded versions of the Mars Microphone sensors placed on the panoramic camera head, enabling stereo recordings of the Martian sounds from a height of about 1 meter above the surface.

In addition to the European Space Agency's interest in listening landers, the Mars Microphone is sponsored by the Planetary Society, UC Berkeley's Space Sciences Laboratory and the Russian Academy of Science's Space Research Institute. Industrial partners include Sensory, Inc and Emkay/Knowles Microphones.

'Feeling' Mars has alot to do with temperature.

The red planet is so cold, that one might have difficulty feeling anything at all. Compared to the Earth's average temperature of 15 C (59 F), Mars globally has an average temperature of -53 C (-63.4 F). While transient temperatures do occasionally rise above water's freezing point in the equatorial regions around both landing sites, almost anything biologically exposed today would quickly dessicate and freeze.

'Tasting and smelling' Mars may offer two intertwined sensory experiences.

Broadly speaking, the red color of martian soil depends on iron oxides, or rust-like conditions, and an even more familiar smell and taste of oxidized metals.

The recent finding that particular locations on Mars-- like the Meridiani landing site--may have very high sulfur content might taint what an otherwise good flavor on the red planet might offer. Sulfur in the form of sulfides can be less than agreeable in high concentrations.

Humans can smell hydrogen sulfide gas, the smell of rotten cabbage or eggs, in the parts per trillion range. Deputy Project Science, Dr. Ray Avridson of Washington University in St. Louis, compared the experience somewhat to a rather corrosive one: "The rocks at Opportunity are sedimentary rocks, shot through by corrosive water, and alot of minerals were replaced, and sulfates precipitated into the pores."

In portions of Meridiani, the apparent concentration of the less odorous magnesium sulfate, or Epsom salts, may be as high as forty percent. The smell of magnesium and sulfate in this form has a rather bland, vaguely metallic and salty character.

So just like bath salts typically require perfuming, the same may hold for how best to get a good whiff of Mars. For anyone who has ever bathed in the Dead Sea, the dry desert salt combination alone has a somewhat suffocating but not entirely putrid quality.

Once the full sensory range is sampled on Mars, at least local portions of the planet would have to be modified to support life in a warmer, wetter environment, one protected against a thin atmosphere and freezing temperatures.

As a new Presidential Commission studies the feasibility of bringing a sample of Mars back to Earth, one can begin to imagine what a full sensory tour of the red planet might translate into--as something akin to a laboratory walkthrough. Like a hospital or scientific laboratory, Mars as we can imagine it today may be relatively sterile, harshly lit, and at the same time, occasionally peppered by odd colors, thinly pitched metal sounds and memorable chemical smells.

Related Links
Mars Rovers at JPL
Mars Rovers at Cornell
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