Every summer since 1997, I have journeyed to Devon Island with colleagues and students from many horizons to study the natural wonders of Earth - and Mars, by comparison. We also test out new technologies and strategies that will help us explore Mars and other reaches of space in the future, with both robots and humans. Our research project is called the NASA Haughton-Mars Project or HMP.
Little imagination is required to believe oneself on Mars when exploring Devon Island. Many features and sites there are strikingly reminiscent of the Martian landscape, from barren rocky blockfields to intricate valley networks, from precipitous winding canyons to recent gully systems on their slopes. We come here to understand whether this resemblance is merely a coincidence or whether there are common underlying causes. Did some of the processes that shaped Devon Island also operate on Mars?
Setting The Stage
It is hard to tell when Devon Island became an island, but the rocks that form the landmass today are mostly ancient seabed material ranging from 570 to 35 millions years in age. The sediments (mostly carbonates) are resting on an even older crystalline basement 2.5 billion years old. Taking this into account, the Haughton impact was a recent event. During the Miocene, the region's climate was much warmer than it is today. Boreal forests of conifers and birch trees covered the land. Giant rabbits and small ancestral rhinos roamed. Local streams and lakes teemed with fish.
All of this changed in an instant.
The object that struck Devon Island was perhaps 1 kilometer (0.6 mile) in diameter. Coming in at cosmic speeds, the impactor delivered a pulse of energy equivalent to 100 million kilotons of TNT. In so doing, it produced a blinding flash of light followed by a monumental air blast that flattened the surroundings, obliterating almost all life several hundred kilometers around. As the impactor itself blended into the target rocks and vanished as a superheated gas, a colossal shock wave expanded into the subsurface. Rocks were crushed, melted, vaporized, and ejected. Soon, a gaping crater 20 kilometers (12.4 miles) wide and 1.7 kilometers (1 mile) deep appeared, only to shallow out moments later as its unstable walls collapsed inwards. As the dust cleared, a smoldering hole filled with a vast pool of chunky molten carbonates appeared. Haughton Crater was born. [More information]
My own interest in Haughton Crater began while I was still in graduate school at Cornell University's Department of Astronomy. I wondered if it would be possible to find an impact crater on Earth in a Mars-like setting - one that could serve as a "Mars analog" for scientific studies and exploration research. Mars analogs are settings on Earth where environmental conditions, geologic features, biological attributes, or combinations thereof offer opportunities for comparisons with possible counterparts on Mars and for partial simulations of Martian conditions.
Haughton Crater is the only impact structure on Earth set in a true polar desert, a place that is cold, dry, windy, barren, rocky, dusty, ultraviolet light-drenched (in the summer), and almost unvegetated. Mars today is indeed also a frigid desert bathing in intense UV with many impact craters on its surface. But the average temperature on Devon Island is only - 17 degrees Celsius (1.4 degrees Fahrenheit), versus - 60 degrees Celsius (- 76 degrees Fahrenheit) on Mars. Conditions on Devon, while extreme by terrestrial standards, are thus far from being as harsh as on Mars. But they are a step in the right direction, and so the site was worth exploring for its Mars analog potential.
To be sure, no place on Earth is truly like Mars. Antarctica is the coldest and driest continent on our planet and remains in many ways of unique value to Mars analog studies. But no positively identified impact structure is known to exist there. Alaska, Arizona, Hawaii, Utah, Iceland, the Atacama Desert, the Altiplano, the Negev, the Sahara, the Gobi, and the Tibetan Plateau, to name but a few classic sites, all present Mars analog aspects. However none of these locations possess the full gamut of Martian characteristics.
Mars analogs can be found above Earth as well at an altitude of 100,000 feet (36,000 m) where the ambient atmospheric pressure (~ 10 mbars) and substantial UV radiation are somewhat similar to Mars. But other elements of the Martian surface environment are missing up there. Thus, a comprehensive Mars analog program is ultimately one that must identify and access not just one setting, but a variety.
The NASA Haughton-Mars Project
This initial reconnaissance trip led to what is today the NASA Haughton-Mars Project, an international interdisciplinary field research project comprising both a science and an exploration program. The HMP science program focuses on learning more about Mars and the Earth, impact cratering on planets, and life in extreme environments. Astrobiology might be the best term summing up the focus of our science studies at Haughton. The HMP exploration program, built around the science program, seeks to develop new technologies, strategies, and experience with human factors that will help plan the future exploration of Mars (and other planets too) by both robots and humans.
The HMP, now in its sixth year and with five consecutive field seasons in the Arctic, continues its research activities on Devon Island. The project draws its core funding from NASA but is actually a collaborative government-private joint venture with substantial support (almost half) contributed from non-NASA sources. It should be added that NASA-funded research on the HMP is not specific to preparing a human mission to Mars. While the science program has a strong Mars flavor, the exploration program is generic in its applicability to planetary and space exploration.
The HMP is managed by the SETI Institute, my home institution and the largest private space research organization in the world. Co-investigators and other participants from a wide variety of government agencies in the U.S., Canada, and other countries, universities and research institutions, private industrial partners, corporations, space interest groups (including the NSS) and exploration societies contribute each year to the project's field activities. [HMP-2001 Supporting, Consulting, Collaborating, Licensing, or Participant Home Institutions]
Each summer, tens of researchers, students, support staff and visiting media join in on field activities. At any given time only 30 people or so are admitted at the field site. A core team of ten individuals spends the entire summer on Devon Island while other co-Investigators and visitors rotate in and out for shorter stays.
High school students from the local Inuit communities of Grise Fiord, Pond Inlet, and Resolute Bay are hired each summer to participate in field activities. College students from both the U.S. and Canada are also offered opportunities to participate in the HMPÕs science and exploration research programs. Logistical support is sought in part from the Polar Continental Shelf Project of Natural Resources Canada, while a research license is issued by the Nunavut Research Institute.
Ground Ice: An Enabler of Human Exploration
As you traverse Haughton Crater you can rove over thick deposits of fused fragmentary debris produced by the impact event. Inside the crater you can encounter ancient lakebeds deposited shortly after the crater was formed. Outside the crater, vast stretches of rocky terrain extend for miles, interrupted only by occasional valleys and steep-walled canyons. Everywhere the ground is laced with subsurface ice.
While rocks on Mars may have a different composition from those found on Devon (carbonates have yet to be unambiguously detected on Mars), the physical properties of impact deposits at Haughton might still provide a valuable analog. It is possible that the distribution of ground-ice in these deposits could help us seek out ground-ice in impact-derived materials on Mars. To date, our ground-penetrating radar surveys and shallow excavations at Haughton Crater reveal that such substrates can hold massive amounts of ice - sometimes more than 80 percent by volume.
The ground-ice on Devon Island and indeed across the high Arctic represents an important repository of freshwater and, as suggested by known examples from Siberia, might even trap a biological record covering several million years. Recent neutron spectrometry data from the Mars Odyssey spacecraft provide startling possible evidence that ground-ice is abundantly present at shallow depth in the Martian subsurface (within the top few meters), particularly at high latitudes. While the findings of the orbiterÕs science team remain preliminary, it appears that ground-ice might also be found at shallow depth at low latitudes in specific areas. If confirmed, this could have important implications both for the search for life on Mars and for planning future human endeavors on the planet. Our studies of ground-ice on Devon could help plan for these exciting activities.
In addition to subsurface ice deposits, Haughton Crater also offers remnant signatures of ancient hydrothermal activity - evidence for which was only recently uncovered by our HMP team. These hot spring features were powered by the tremendous amount of heat dumped into the surrounding rocks at the time of impact. While the impact-induced hydrothermal activity has long ceased, the hydrothermal sites are preserved in almost pristine condition, having been spared substantial weathering due to the increasingly frigid climate that has prevailed in the Arctic since the Miocene.
Understanding the nature, evolution, location, and preserved record of impact-induced hydrothermal activity at Haughton Crater helps us assess the biological potential of similar sites on Mars as well as on other planets. Impact-induced hot springs would have been places where liquid water and warmth would have coexisted, if only for short periods. As such, they are places where life, perhaps imported from elsewhere, might have gained a foothold and thrived.
Haughton Crater also once contained a lake - or, to be more precise - a network of water bodies whose shapes evolved over the course of time. These bodies of water formed very shortly after the crater's formation and may have lasted only a few million years. Although the lake waters are long gone, sediments were laid down that are beautifully preserved. These paleolakebeds represent the only sedimentary record of the Miocene preserved on our planet in the Arctic. As such, they provide us with a unique view of what conditions in the Arctic were like 23 million years ago.
It is within Haughton Crater's ancient lakebeds that our colleague Leo Hickey of Yale University and his collaborators found the remains of Miocene plants and animals. The remains are almost intact. Bone has not been transformed into stone (petrified), but is still bone. Similarly, wood found in the lakebeds is still wood. In addition, the fine, silty layers that serve as a detailed climatological record of conditions within the crater, are hardly disturbed. These findings in the Arctic offer the hope that craters on Mars might preserve well-preserved paleoenvironmental records as well.
Using Haughton Crater To Reveal Ancient Martian Climate
Taken in a broad context, the overall amount of erosion we find at Haughton Crater might be telling us something important about Mars. In spite of HaughtonÕs young age compared with that of many similar-size craters on Mars, it is far less well preserved than its Martian counterparts, most of which are probably between 2.5 and 3.8 billion years old. At the very least, the cumulative effect of erosion on Mars in the past 2.5 billion years appears to have been less than that experienced by Haughton in the Arctic over the past 23 million years.
Thus, average erosion rates have probably been over 100 slower on Mars than in the Arctic on Earth. This would lead one to expect that if Mars was ever wet and warm at any point over the past 2.5 billion years at least, it was probably not so for very long. Otherwise, more erosion would be in evidence on Mars.
Many features outside of Haughton Crater itself are also contributing to solving, and sometimes deepening, the mysteries that Mars presents to us.
Networks of channels found on Devon Island bear similarities to the so-called Martian small valley networks. On Mars, most of these features date back to the end of the "Heavy Bombardment" (a period of high impact rates early in the history of the solar system). Some of these features are also found on more recent Martian terrains such as the flanks of relatively young volcanoes.
The classical interpretation of the Martian small valley networks is that they are the result of liquid water runoff flowing across the Martian surface. This is thought to have occurred not in the form of gigantic floods (as in the case of the Martian outflow channels), but rather, as more modest trickles. The small valley networks are thought to have formed from the action of either localized rainfall, groundwater or ground-ice release, or from various forms of mud flows. All of these interpretations require a fairly warm climate on Mars for liquid water to flow (without freezing) over distances of tens to hundreds of kilometers.
The surface of Devon Island has been carved by a multitude of small valley networks that bear an uncanny resemblance, including in their bizarreness, to the many small valley networks on Mars. Curiously, when you consider the classical explanations for Martian small valley networks, the Devon Island networks formed neither by rainfall, groundwater or ground-ice release, or mud flow. Rather, they were formed by the melting of vast ice covers that once occupied the land above the material exposed at the surface today.
Given what we see on Devon Island, is it possible then that the many small valley networks on Mars were actually formed under a frigid climate rather than under a warm and wet one? Might Mars have been cold climatically throughout most its history, with liquid water at most a local and transient phenomenon at the surface?
While not settling the mystery of past climates on Mars, our work on Devon Island is offering new interpretations for many of the planet's so-called "fluvial" landforms. Our research suggests that surface ice deposits on Mars may have played a much greater role throughout Martian history than has been suspected in the past.
There are many other features on Devon Island with eerily similar counterparts on Mars, including vast canyons and small gullies. In the end, it is perhaps not any single parallel that should impress, but the convergence of so many in a single small area of our planet. Without loosing sight of the fact that no single Mars analog on Earth can be considered ideal (it depends a lot on what one wants to study), Devon Island has come to be described by many as, and granted with much exaggeration, "Mars on Earth".