The first successful probe to Mars was Mariner 4 with a flyby on July 14, 1965. We have been exploring Mars with increasing fervor ever since. Launch windows open every 26 months and July 2020 saw the largest fleet of Mars probes ever launched in an international competition to explore the mysteries of the Red Planet. Developed by University of Colorado, Boulder; Arizona State University and University of California, Berkeley, the United Arab Emirates launched its Hope Mars orbiter on July 19 on a Japanese booster. On July 23, China launched its Tianwen-1 orbiter and lander/rover.
Last but not least, on July 30, NASA’s Jet Propulsion Laboratory launched the Mars 2020 Perseverance rover. Perseverance is destined to land at Jezero crater on Feb. 18, 2021, with the most sophisticated kit of geology tools ever assembled for an astrogeology mission. The rover will explore ancient deltaic deposits that formed in a long-lived lake in the crater searching for signs of life that may have evolved there. The rover will cache samples to be returned to Earth on a future robotic mission for detailed study in preparation for landing humans on Mars.
AAPG, as an institution dedicated to exploring for resource commodities, looks to our future in space through the Astrogeology Committee and the Energy Minerals Division. We emphasize the use of geosciences in the development of off-world exploration energy and other natural resources for development in the foreseeable future. Water resources in space, on the moon and on Mars, will become the energy commodity analog of oil on Earth. Astrogeologists are mapping Mars water resources and planning to use Mars’ regolith as a resource to support a closed ecosystem for human colonization. Using today’s technology, we can seriously think about sending humans to Mars. The Red Planet has the resources. We must learn how to live off of the land to have a sustained presence there.
For inspiration to go to Mars, we look to our innate nature to explore. Apollo 17 Commander Gene Cernan said, “Inspiration, sweat, challenges, and dreams got us to the moon and they will get us to Mars and beyond. It is our destiny.”
SpaceX CEO Elon Musk, is dedicated to enabling humans to colonize Mars, perhaps in this decade. He said, “The future of humanity is to become multiplanetary, or it’s going to remain confined to one planet and eventually there’s going to be an extinction event.”
We wistfully look back at the Apollo 11 moon landing 50 years ago, but no time since has offered so much promise for human exploration of deep space. On Dec. 17, 2017, President Trump signed Space Directive 1 that calls for a United States-led return to the moon followed by human missions to Mars. Vice President Mike Pence, as chair of the National Space Council, has called for a human return to the moon by 2024 to pave the way for sending humans to Mars. The intent is to have a sustained presence on the moon by 2028 in preparation for sending a crew to Mars by the mid-2030s.
NASA is not only following this path with traditional contract partners such as Boeing and Lockheed Martin. The arena also involves international partners, such as the European Space Agency and other industry partners such as SpaceX and Blue Origin.
NASA Administrator Jim Bridenstine said, “The reason we need commercial operators is because they can drive innovation by competing on cost and innovation.”
Space has also become an arena for entrepreneurs. According to a report from investment firm Space Angels, private investors poured $3.9 billion into commercial space companies in 2017.
Water is the New Oil
The NASA Mars Design Reference Architecture Mission Profile uses the Space Launch System and commercial heavy-lift vehicles to place cargo and a crew habitat on Mars before sending a crew there 26 months later at the next launch window. NASA calls for the first crew landing to have a fully fueled return vehicle waiting for them on the surface. Later, sustained presence leading to a Mars colony will require accessing Mars’ in situ water ice resources for drinking water, oxygen to breathe and to manufacture propellant. SpaceX proposes to send its radical new reusable Starship design to the surface of Mars to begin colonization. It will require refueling with Mars-derived propellant to return to Earth.
Water is an increasingly valuable commodity not only for staying on Mars but for any deep space operations. Water and energy are the raw materials that will make all long-term activities possible on Mars, the moon or anywhere outside low Earth orbit. We need water for life and it can provide oxygen to breathe. Water can be used to produce hydrogen and oxygen for rocket propellant. It can be mined for example, on the moon, on asteroids and on Mars. Someday, water will be an interplanetary trade commodity much more valuable than crude oil on Earth.
The average lifting cost today to get any mass out of Earth’s gravity well into low Earth orbit is about $35,000 per kilogram. Reusable lift vehicles will change the game. The cost of lifting water and propellant can be greatly improved with reusable lift vehicles. In the near future they could reduce the lifting cost to $1,880 per kilogram. Compare this to the cost of crude at about $0.60 per kilogram. Water as a resource in space could be worth more than a thousand times the value of crude on Earth.
So what about water on Mars, the red desert planet? The image at the top from NASA’s Curiosity Mars Rover clearly shows cross-bedding in the layers of this Martian rock as evidence of flowing streams in loose sediment in the first billion years of Mars’ geologic history.
This Mars digital elevation model from laser altimeter data from Mars Global Surveyor shows the low elevation, smooth northern hemisphere that once held an ocean from about 4 billion to 3.7 billion years ago.
The Tharsis Bulge is a volcanic area that was active in that time frame. This includes Olympus Mons, the largest volcano in the solar system. Scientists suggest that Tharsis volcanoes spewed gases into the atmosphere that created a global warming greenhouse effect that allowed liquid water to exist on the planet. Also, the volcanic eruptions created channels that allowed underground water to reach the surface and fill the northern plains.
Where did all of Mars’ water go? NASA’s MAVEN, or Mars Atmosphere and Volatile Evolution probe, arrived in Mars’ orbit in 2014 to study the Martian atmosphere. It confirmed that most of Mars’ atmosphere and much of its water was stripped away by the solar wind and extreme ultraviolet radiation ionization. Mars has no appreciable magnetic field, as the Earth does, to protect it from high-speed charged particles in the solar wind.
Remote sensing and direct Mars observation shows that there is appreciable near-surface and underground ice on Mars. The ice may be layered and pore filling and in some cases water ice forms massive underground ice glaciers. Mars Phoenix Polar Lander scooped into the soil and revealed water ice directly at 68 degrees latitude near Mars’ north pole in 2008. Water ice exists in free-form in shallow soils in the polar areas north and south of the 60 degree latitude lines, and in massive isolated but buried glaciers in some locations equatorward of these areas. Shallow soils nearer the equator contain huge volumes of water locked in water-bearing minerals that can be exsolved by simple heating.
High-resolution orbital imaging offers us new insights into the nature of subsurface ice. HiRISE (High Resolution Imaging Science Experiment) imaging from the Mars Reconnaissance Orbiter provides evidence and details. Water ice is seen in impact craters and erosional scarps.
Terraced craters are windows into Mars’ icy past. Just beneath the Mars’ surface soil and regolith in mid-latitude Arcadia Planitia, University of Arizona researchers found an enormous slab of water ice. It measures 40 meters thick between the upper wall terrace and floor terrace of the observed craters. The buried ice slab covers an area equivalent to that of California and Texas combined.
This steep scarp, imaged by MRO, formed by mass wasting at 55 degrees south latitude. The scarp directly exposes shallow pure water ice. The identification as water ice is confirmed by the gamma ray spectrometer, GRS and CRISM (Compact Reconnaissance Imaging Spectrometer) on MRO. The scarps expose deposits of water ice that can be more than 100 meters thick, from depths as shallow as 1 to 2 meters below the surface. The scarps are retreating because of sublimation of the exposed water ice, according to a 2018 paper by Colin M. Dundas in Science, “Exposed subsurface ice sheets in the Martian mid-latitudes.”The accompanying image from Arcadia Planitia area of Mars shows many surface bulges from widespread subsurface ice pingos similar to permafrost areas on Earth. Nearby areas show near surface glacial ice flows. The pervasive shallow ice in Arcadia Planitia make this mid-latitude area a possible site for a base for sustained human presence using the in situ ice resources. The presence of ice is corroborated by Mars Odyssey probe’s gamma ray spectrometer.
Approximately five million cubic kilometers of ice have been identified at or near the present surface of Mars. GRS from the Mars Odyssey probe, ground penetrating radar, SHARAD and HiRISE imaging from the Mars Reconnaissance Orbiter provide evidence and details.
SHARAD sent radar pulses to the surface then processed them as images – similar to a seismic line – as seen above. Vast deposits of water layered with dust appear to be trapped within the ice caps at the north and south poles of the planet. Each summer, as temperatures increase, the caps shrink slightly as their contents sublimate straight from solid to gas form. In the winter, cooler temperatures cause them to grow halfway to the equator. The caps are an average of 3 kilometers thick and, if completely melted, could cover the Martian surface with about 5.6 meters of water. In fact, the European Mars Express spacecraft used its MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) ground penetrating radar and detected liquid water below the south polar cap of Mars.
How will we extract and utilize water on Mars? This is the realm of technology entrepreneurs. One can envision drilling and using microwaves to extract water, augers to bring ice to the surface for processing, or even larger scale surface mining operations.
Powering the Mars Missions
It is unlikely that such operations will be solar powered. NASA has developed and demonstrated a uranium sourced Kilopower system, also known as KRUSTY, Kilopower Reactor Using Stirling Technology. The Kilopower reactors will come in scalable sizes able to produce from 1 to 10 kilowatts of electrical power continuously for 12-15 years. The fission reactor uses readily available uranium-235 to generate heat that is carried to the Stirling converters via passive sodium heat pipes. The Kilopower reactors can be set up in clusters to increase available power.
The Mars Society founder Robert Zubrin proposes in-situ propellant production on Mars by combining 8 metric tons of hydrogen brought from Earth with Mars atmospheric CO2 to produce 112 metric tons of methane and oxygen for a crew Earth Return Vehicle. The Sabatier reactor required for this could be powered by a 100-kilowatt nuclear reactor taking 10 months to produce the 112 metric tons of propellant. With the availability of ample power and water, there is no need to import the hydrogen – it would be a readily available by-product of the electrolysis of water to produce both oxygen and hydrogen.
SpaceX’s business model is to develop the reusable super heavy booster first stage and Starship second stage for heavy cargo and crew lift to low-Earth orbit and beyond. Eventually, the Starship will be refueled in Earth orbit and used to send colonists to Mars. Returning the Starship to Earth will require refueling it with up to 1,100 metric tons of methane and liquid oxygen using Mars in situ resources.
Manufacturing that much propellant requires an enormous 10 gigawatt hours of electricity to power electrolysis of water ice to produce hydrogen and oxygen, to power a Sabatier reactor to produce methane from hydrogen and Mars atmospheric CO2, and to liquefy the methane and oxygen for Starship fuel, according to a 2017 paper by Patrick Ray Mcclure, “Space Nuclear Reactor Development,” published in Nuclear Engineering Capability Review.
Ten combined 40-kilowatt Kilopower units would produce 0.4 megawatts of electricity and take 2.8 years to make 1,100 metric tons of liquid oxygen and methane. Clearly a larger reactor system will be needed for such a task. Lawrence Livermore National Laboratory has developed a portable uranium reactor design called SSTAR (Small, sealed, transportable, autonomous reactor). It might be feasible to construct a 10-megawatt system that could be transported to Mars on a SpaceX cargo Starship. Such a powerful system could produce the 1,100 metric tons of propellant in just four months and provide power for a large growing Mars colony.
Could we one day mine uranium on Mars for our energy needs there? The formation of Earth and Mars as terrestrial planets suggest that they should have similar mineral resources, having formed in the same inner realm of the original solar nebula. A gamma-ray spectrometer map of thorium, a daughter product of uranium decay on Mars, serves as a proxy for the abundance of uranium on Mars. The richest thorium/uranium resources mapped on Mars are in Mare Acidalium and Utopia Planum, where the northern ocean of Mars once existed. Early Mars hydrologic processes may have concentrated uranium in these areas just as we see uranium concentrated by precipitation from water on Earth. The Zagami meteorite is a piece of basalt that was blasted from Mars and landed near Zagami, Nigeria. This small sample of Mars confirms uranium on Mars at a concentration of about 0.1 parts per million.
Toward Sustainable Colonies Beyond Earth
The most critical resources for humans on Mars are water and energy. We have seen that water is present in abundance if the landing zone is well chosen. Technology exists for nuclear power that is transportable to Mars. The first humans to Mars will have to bring all of their food consumables to last until resupply arrives from Earth. Eventually reliable self-sustaining facilities to grow food will be developed relying on water and energy resources perhaps aided by fertilizers derived from mining the resources on organic rich asteroids or moons of Mars.
The AAPG Astrogeology Committee and Energy and Minerals Division are looking ahead to the evolution of our organization. Energy and exploration have always been our reason for being, and we see only opportunities as we reach out beyond the Earth. We have developed our expertise in looking inward to observe and define subsurface processes. Our future and our destiny are now to look outward and explore and develop a sustainable presence in the solar system beyond Earth. Mars and the moon will become a second and third home for humanity. The resources for human settlement are there for those with the entrepreneurial spirit to get in on the boom.