At our morning meeting I laid out our plan for the next several days: a series of long-range motorized reconnaissance EVAs to give us a broad familiarity with the area and identify key sites for further in-depth study. One of the crew members asked if it might not be more methodical to start at the hab and slowly spiral out, studying one site after another in turn. My response was no: When you explore a house you don’t walk in the front door and then stop and spend several hours examining the contents of the foyer with a microscope. No, you give the place the once-over first. It is the same with field exploration. Before you invest a lot of time in focussed study of particular sites, you conduct a general survey. This gives you the overview you need to assign your priorities.

The EVA team was composed of Steve McDaniel, Jennifer Heldmann, Heather Chluda, and yours truly. With four people going EVA it took a while to get everyone suited up, so we were not out the lock until a little before noon. We took about 20 minutes to set up a weather station, and then headed north on our All Terrain Vehicles (ATV’s).

ATV’s are like four-wheel drive motorcycles. Your ride them in equestrian fashion, with a single rider astride each one. They allow you to travel fast over very rough terrain, and are light enough that if one gets stuck, you can probably liberate it using human labor power alone. The air/fuel combustion-engine powered ATV’s that we drive on Earth won’t work on Mars, but equivalent vehicles driven by fuel cells could be created and should be. Because while minivan-sized pressurized rovers will also play a role in Mars exploration, it will primarily be as mobile bases – they simply won’t have the agility needed to deal with most types of unimproved ground, and in any case, the idea of going through all the work of suiting up for a pedestrian EVA whenever a pressurized rover reaches an interesting site is unappealing. No, Mars explorers will need the kind of informal mobility that an ATV can provide, moving them directly where they want to go while keeping them in intimate contact with the environment.

The weather was perfect. We set out heading north, and after traveling about 2.5 kilometers came across a rather impressive outcrop of sedimentary rocks. We decided to check it out. Jennifer, our geologist, and Steve, our biologist collected all types of samples of rocks and possible cyanobacteria. I searched the place for fossils, but didn’t find much. This was a disappointment. The banded Mesozoic sediments included both terrestrial and marine materials, and wave ripples in the sandstone were clearly visible. By rights, the formation should have been full of fossils. It wasn’t.

We continued north another 2.5 kilometers and came to a hill too steep for the ATVs. I decided to climb it, though, to get the view of the region to the west. We hiked up, and were rewarded not merely with an impressive view, but with the sight of a fair-sized canyon and a passable ATV route to get there.

So to the canyon we went. This was a wonderful place, with a steep little gorge that exposed millions of years of banded sediments to easy view. I climbed around the rim and had a Eureka moment when I found some bits of petrified wood. These however were made irrelevant within minutes by Heather who found a small mountain made of the stuff. – in several varieties no less. But then I found something which really made my day – a bone of stone. It’s the size of a coffee-mug, and the indentation for the joint is clearly visible. The material I found it in was Jurassic, so my guess is that it’s a dinosaur.

We won’t find dinosaur fossils on Mars, or even petrified wood, but we might find stromatolites or other types of primitive fossils, and the issues involved are similar. Fossils finds are anomalous phenomenon. For one to occur several unlikely things need to happen. First, an organism which, as a living thing, must live its whole life in contact with the biosphere, must be isolated from the environment at the moment of death. This is necessary or the environment will destroy its remains. It must then remain isolated from the environment for millions or (in the most probable case for Mars) billions of years, only to be exposed the environment again right before you show up. If it is not re-exposed you won’t find it, and if it is re-exposed too soon it will be destroyed before you see it. If all this seems rather improbable, it is. That is why we are not all constantly tripping over Triceratops bones. And that is why fossils will be at least as rare on Mars as they are on Earth.

There is a lesson in all of this for those who think that robots represent a superior way of exploring Mars. With a human crew on this site, impaired by all the impedimentia of spacesuit simulators with the cloudy visors, backpacks, thick gloves and clumsy boots, our crew found petrified wood and a fossil bone fragment within two days. But to do it we had to travel substantial distances, and climb up and down steep hills from which we could take views and map out new plans. We had to search the sites we visited, processing the equivalent of millions of high-resolution photographs with our eyes for subtle clues. We had to dig. We had to break open rocks and take samples back to the station for detailed analysis. In short, we had to do a ton of things that are vastly beyond the capabilities of robotic rovers.

Sojourner landed on Mars and explored 12 rocks in 2 months. Today we explored thousands. If a robot had been landed at the position of our hab, it would have spent months examining a few uninteresting rocks in the immediate vicinity of the station. It would never have found the fossils.

After the canyon, we continued further north, eventually coming to a huge cliff, with a 500 ft sheer drop past several epochs of exposed geologic history. The view was spectacular. Heather suggested we rappel down. That’s the sort of thing she goes in for. Fortunately, however, no rope was available, and we all returned to the hab alive, having covered 19 kilometers in a day…