The only scientist and field geologist to visit the moon offers advice to those who will one day visit Mars
By Harrison H. Schmitt
Mountains taller than the walls of the Grand Canyon of the Colorado River towered above the narrow Taurus-Litro Valley. A bright sun, brighter than any sun that had ever been seen on earth, illuminated the cratered valley floor and the steep mountain slopes, which stood out in stark contrast to the pitch-black sky. The valley, which is about 4 billion years old, is partly covered by lava and ash rocks that are slightly younger than it. My teammate, Eugene Sarman, and I explored this valley for three days in 1972 on the final mission of the Apollo program. It was the first time, and the only time so far, that a geologist conducted field research in another world. The USA, the European Union, Russia and other international partners are currently considering sending astronauts for space research on Mars, which will probably begin during the first third of this century. When the first geologist stands in front of the sunrise on Mars, what will be new for him and what will be familiar?
Most reports on the Apollo missions focus on their historical firstness and high-tech achievements. But we, who participated in them, also remember the simple, less glamorous human sides: walking on the ground, breaking pieces of rock with a geological hammer, dragging rocks and generally managing in the foreign conditions. Any geologist will recognize the principles and techniques of the field research we conducted. The basics were no different. There, too, the goal was to document and visually represent the structure of the natural terrain, their relative age and change in order to determine what their origins are and what resources they may one day provide to our culture. Leaving Earth did not change the principles of planning an exploration expedition and carrying out its mission, such as how to collect samples and document them. If anything, these principles became more important because the chance of returning to the same place was lower. In particular, there has been no change in the need for human contact, experience and imagination to fully appreciate the scientific and human values of research.
In any new place that humans will explore, we will have to rely on our experience in exploring the last place we were before, as geologists have done on Earth for more than two centuries. We must constantly ask ourselves what might be similar and what might be different. How will the geology of Mars, accessibility, exploration strategy and the optimal composition of the crew to be sent there compare to the experience gained in the Apollo program?
in the field on the moon
Very complicated factors affect the geological structures on Earth. The crust, the magma, the water and the atmosphere act on each other. Marine and continental plates are breaking and colliding. Objects from space hit the earth. And the biosphere, which includes humans, changes the landscape. On the Moon, most of the factors that affected the surface during the last four billion years were external factors, and even these were mainly limited to the impacts of bodies and high-energy particles that make up the solar wind.
The absence of an atmosphere exposes the materials on the lunar surface to the extreme vacuum conditions of space. Comets and meteors, some of them as small as dust grains, moving at speeds of tens of kilometers per second, strike rocks, rock fragments, glass and lunar dust and change them. This process created on the moon what can be called "soil": a layer of broken and semi-vitreous remains, known as lunar regolith. The regolith covers most of the older volcanic flows and impact craters as a blanket several meters thick. Field exploration on the moon therefore requires a geologist to have vision similar to an X-ray. In order to identify the contact zones between main rock units, I had to imagine how the original contrast of the color and texture of the minerals in the rocks was smeared and blurred due to collisions from space that created regolith and caused its gradual expansion.
For example, in the Taurus-Litro valley, I uncovered a contact zone between two types of rocks: a dark, fine-grained basalt rock and a broken, gray, older rock called breccia that was formed by an impact from space. When this contact zone between the rocks formed, it must have been sharp: a rough seam between the two types of rocks. But 3.8 billion years of exposure to outer space has spread that seam over several hundred meters. Whereas in another place, the contact zone between sediment formed in a landslide and the dark regolith has been spread over only a few dozen meters in the 100 million years that have passed since the landslide occurred. Because I understood the processes that actively change these contact zones, I could determine their original location. Similarly, a geologist on Earth must determine how the erosion of soils in our own world obscures or covers contact zones and rock formations.
In order to identify in the field the different types of rock that make up the exposed rocks on the surface of the moon, it was necessary to understand the effect of the incessant bombardment of micro-meteorites. When particles hit the terrain at extreme speeds, they create a high-temperature plasma, which is concentrated in one place, and melts the rock at the points of impact. The plasma and molten rock spewed from there recrystallize on the surface of the rock surfaces adjacent to the collision site. This creates a thin, vitreous and brown coating, known as patina. This coating, which contains tiny iron particles, over time covers the entire surface of the stone. Just like a geologist on Earth who has to peer through the desert coating that covers bare rocks in arid regions of our world, I had to scan the stones quickly with my eyes and guess what lay beneath that patina, even before I could break a chip from the stone with a hammer.
Small impact coils that break the lunar patina contain glass in a variety of shades, reflecting the different chemical compositions of the minerals struck in the collision. When the shale is formed of a white mineral (such as plagioclase feldspar, a main component of volcanic rocks), it contains a light-gray glass and a characteristic white stain caused by thin cracks that break the mineral grains. When the damage is to a mineral rich in iron or magnesium, green glass is formed. Thanks to this familiarity with the process, observing the rock was enough for me to determine its composition.
What will the researchers find on Mars?
The Red Planet is larger than the Moon and smaller than the Earth, so the scientists expect to find that it was affected by a combination of the factors that acted on the Earth and those that acted on the Moon. Indeed, our accumulated geological knowledge of Mars has already confirmed this combination of processes. Already from the first images received from spacecraft that orbited Mars and from the Viking 1 and 2 spacecraft that landed on it, we knew that the geological features of Mars were created by a combination of internal and external factors.
Unlike the Moon, Mars has a thin atmosphere. The pressure on its surface is about 1% of the pressure prevailing at our sea level. The existence of this atmosphere changes the geological pattern that researchers will have to take into account when they come to identify, analyze and understand the rock units beneath their feet. The atmosphere filters and removes small meteors and comets capable of creating craters less than 30 meters in diameter. The surface is therefore not covered with impact splashes like the moon is. Instead, the traveling material on Mars is wind-borne dust. The dust comes from various sources, such as rocks eroded by the wind, landslides, impacts from space and chemical reactions. It creates soft ridges (dunes) that researchers would prefer to avoid, just as we avoid snowdrifts piled up by the wind on Earth's plains and mountain passes. Indeed, the Spirit and Opportunity SUVs sometimes got stuck in the dirt [when translating the article, the Spirit SUV is stuck in such a trap - the editors].
Despite the filtering effect of the atmosphere, the surface of Mars, and the material close to the surface, are mainly affected by geological processes related to impact from space. The first geologists will therefore have to decipher the effect of the splashed material, the fractures and the shock waves on the rocks. But not all rocks are related to impact from space. Layered rocks similar to sedimentary rocks and volcanic layers dominate geological rift valleys and other regions of Mars. The regolith formed by impacts from space is not continuous, and many original Martian rock formations protrude from the surface and allow access for geological exploration and routine sample collection.
The moon is dry, but on Mars liquid water has shaped the surface and created new minerals. Laboratory testing of rock samples from the moon did not identify minerals formed in water. But space sensors and robotic chemical analysis of minerals on Mars have identified a variety of water-bearing clays and sulfate salts that likely sank in water. Moreover, the rocks on the Moon contain unoxidized metallic iron, while on Mars there are extensive deposits of oxidized iron (hematite, Fe 2O3), further evidence of the action of liquid water [see "Water in the Past of Mars" by Jim Bell, Scientific American Israel , April-May 2007; "The Many Faces of Mars" by Philip R. Christensen, Scientific American Israel, October-November 2005]. The geologist who will be sent to Mars will have to prepare to decipher a much wider range of minerals than those we found on the moon. Water also transports matter from place to place. In some ravines and impact craters it appears that the underground ice that melted created mudslides.
In short, the Martian regolith usually contains layers of material splashed by impact from space and remnants of mudslides or floods and layers of wind-borne dust. In the polar regions it also contains water and carbon dioxide frozen in ice and frost, as confirmed recently by the Phoenix lander. The complexity of the regolith on the moon did not come close to this.
As a result of these differences between the Moon and Mars, the field geologist will have to face new challenges on Mars. Here, too, the researcher will have to develop penetrating X-ray vision, but it will be similar to that required on Earth, meaning that you will have to take into account the effect of wind, gravity and materials that have been swept away by water. But in other respects, the exploration of Mars will be easier than the exploration of the Moon. Images from Mars show that although the wind-borne dust creates a very thin, patina-like coating on many rocks, the wind often cleans the surfaces. The dust cover will therefore not interfere with the evaluation and identification of minerals at a glance.
One point of similarity to lunar exploration would perhaps be the problem of visual distortion. In a vacuum, or in thin atmosphere conditions, our brains tend to underestimate distances. We also experience this in the clear air of the desert or in the mountains on Earth. The absence of familiar objects, such as houses, trees, bushes, electricity poles and the like aggravates the situation. Neil Armstrong was the first to notice the problem after he landed Apollo 11. I learned to correct for the phenomenon by comparing the known length of my shadow to what I actually see and then increasing my distance estimates by about 50%.
The dirt on the surface will also deceive the eyes. On the moon it caused a strong backscatter of light whenever we looked in the exact opposite direction to the sun. This phenomenon, called the opposition effect, looks like a bright and blurry spot of light. The same phenomenon occurs when we observe our own shadow on the surface of the snow or the shadow of the plane we are flying in as it passes over a green forest or agricultural fields. Even astronauts on Mars will see it. This backscatter brightens the shadows a bit. On the other hand, when looking in the direction facing the sun, the shadows are illuminated only by the light reflected from other objects standing on the surface. We had to adjust the opening of the aperture in our cameras according to the direction of the sun in each shot. The research cameras and the future video systems will be able to adapt themselves to the lighting conditions automatically.
Personally, I was very comfortable on the moon. I attribute this level of comfort to the fact that I was highly motivated, well trained and had a lot of trust in the support team on Earth. But the moon is only three and a half days away from the earth. On the other hand, Mars, if we fly to it using normal chemical rockets, is at least eight to nine months away. Even using a nuclear fusion engine or electric drive to accelerate or decelerate the spacecraft along the entire trajectory, the journey would take months. Because of this isolation, the Mars crew will have to rely on themselves much more than the Moon crews did.
But even so, I don't think that psychological issues will cause any particular difficulty. An extended return period of a few months, as opposed to a few days, can have a negative effect on some people, but Earth's explorers have also overcome tougher challenges than that. Throughout history, adventurers have gone through periods of distance from home similar to those expected for the first crews on Mars, and without any means of communication. The motivation, training, trust between crew members and sense of survival of the astronauts for Mars will be quite the same as those of the Apollo astronauts. Each of them will be very busy operating the spacecraft and maintaining it, scientific missions, fitness exercises, simulation training for their future missions, updating the research plans and many other duties. In fact, if the history of spaceflight is anything to go by, finding time for themselves to rest may be crew members' greatest psychological challenge. The planners on the ground will have to take this into account.
The main limitation to effective research on Mars, as it was on the Moon, would be the need to wear a pressure suit. The Apollo spacesuit, model A7LB, that we used in the Taurus-Lytro study allowed us to do an impressive amount of field work in very hostile conditions. The pressure in the suit was about a quarter of the atmospheric pressure at sea level on Earth. If necessary, I could run it at a speed of about 10 km/h at an even pace and for a distance of several kilometers, in a walking form adapted to cross-country skiing. Using the equipment we had and teamwork we were able to collect samples, record them on camera and put them in a backpack at a reasonable pace. During our 18 hours of research we collected more than 110 kilograms of rocks and regolith. I would have been happy if I had more freedom of movement in my legs, waist and arms, but we managed well even with the freedom the A7LB gave us.
The thing we almost didn't get along with, or at least the thing that caused us considerable fatigue and damage to our hands, was the gloves. Something must be done to improve glove technology when we go back to the moon and go to Mars. Finger flexibility was limited, and my wrists got tired after about 30 minutes. It was like squashing a tennis ball endlessly. Eight hours of rest was enough for me not to feel even the remnants of muscle pain, one of the advantages of more efficient blood circulation in conditions of one-sixth gravity. But after eight to nine hour hikes in the pressure suit, I don't know how many more tours I could take with the bruises on my hands and the damage to my nails caused by the gloves.
Space suit technology will perhaps develop to a level where the gloves, or their equivalents, will allow action similar to a free hand and that the suit itself will allow movement like cross-country ski clothing. It is conceivable that robots will help in the field to plan the journeys in advance. Moreover, based on the experience acquired by the astronauts who assembled the International Space Station, we know today physical training methods that improve the preparation of the hand muscles for continuous effort. Additional new procedures and equipment details could further improve research efficiency.
The political urgency and nature of the test flights in the early planning stages of Apollo made it possible to select only a few geologists experienced in field work as full members of the lunar mission teams. NASA chose mostly experienced test pilots and fighter pilots and only one field geologist with flight training (me). All crew members had to be experienced experts and confident in operating the equipment and methods necessary for flight. There was no place for a field geologist as a "passenger".
This should be changed with the return to the moon as part of the Constellation program in about 10 years. Professional space explorers must be sent in all the teams that will go to the moon, as a precedent for the exploration of Mars. As with the last Apollo missions, all crew members and their operational support teams will undergo as much training on Earth as possible in solving geologic problems in the field. It seems that the optimal number of team members for the first research missions is four: two professional pilots who will receive additional training as field researchers and systems engineers, as was the case with the Apollo teams; One professional field geologist who will receive additional training as a pilot, as a systems engineer and as a field biologist; and one professional field biologist who will receive secondary training as a doctor and field geologist.
This combined training will mean that the success of the mission will not depend on one person but on teamwork. It is necessary that the members of the Mars team be willing to contribute their specialist skills to the combined team, and in addition to this, each of them must also comfortably and without reservation accept the hierarchical command structure. Throughout history, small and isolated teams of explorers achieved the greatest success when they operated under the direction of a clear and experienced leader.
Mars exploration will differ in many aspects from lunar exploration. First, the trip will last months, not days, and the crew will therefore have to continue to practice landing and other flight procedures throughout the entire journey. In the Apollo missions, we practiced the landing in a ground imaging device, and our last "dry" training was a few days before liftoff, less than a week before we were supposed to begin the powered landing on the moon. The time gap between takeoff and landing on Mars will be about nine months, undoubtedly too long without regular practice on board the spacecraft.
Second, ground control on Earth will not be able to perform its traditional tasks due to the long delay in communication (up to 22 minutes one way). On Earth, they will instead engage in activities that do not require live contact with the team, such as data analysis and integration, weekly planning, control and analysis of the systems and the materials the team needs, planning maintenance operations and developing future scenarios. The real-time control operations will have to be performed by the astronauts themselves. For example, the mission can include two crews, one will land while the other will remain in orbit and act as a control center in space. When the first team returns to orbit, the second team will land to investigate another site.
There were already precedents for such a level of autonomy. Even in the Apollo program, although we had pre-planned the research operations we would conduct on the moon even before takeoff, using photographs we had, NASA left the teams considerable freedom of action to take advantage of opportunities to work on unexpected targets. For example, near the end of Apollo 17's second exploration tour, when we only had 30 minutes left to work, I discovered orange volcanic glass on the side of Shorty Crater. Without waiting for suggestions from the control, Eugene and I started writing a description, photographing and sampling the deposit. We didn't have time to discuss this plan with the members of the control team, but we knew immediately what we had to do. Just such an approach will be required all the time from the members of the crew to Mars. The control people on Earth, on the other hand, will find out anything tens of minutes after it happened.
And there is also a third difference between Mars and the Moon. Given the financial cost and historical importance of any exploratory mission to Mars, the philosophy of the mission will be absolutely oriented towards achieving success. Even if something goes wrong, the astronauts must be able to continue the mission and achieve its primary goals. For example, it is desirable for the ship to carry two landings, in case it is not possible to use one of them. Moreover, if a systems or software failure occurs during orbit entry, descent or landing, the astronauts will need to be able to abandon the lander and land, rather than abandon and take off back into orbit, as was planned in Apollo. Then it will be possible to solve the problems in consultation with Earth, after the team has already landed safely on Mars.
The young people alive today will have the opportunity to participate in the adventure of exploring Mars, if their parents and grandparents provide them with the opportunity to do so. It won't be easy. As with anything worth doing, there are risks here too. On the one hand, the reward from the expansion of knowledge will be enormous, and on the other hand, the price we will pay for ceasing our research and discovery will also be enormous. Postponing the exploration of Mars to a later date than is planned today, will leave the Americans trailing behind other explorers and other nations. Moreover, without a gradual and continuous effort to learn how to explore other worlds, and eventually colonize them, the very existence of the human race will remain subject to the threat of being struck by asteroids or comets traveling through the solar system. Curiosity, the lessons of history and our instinct for existence compel us to continue forward.