A violent past
Approximately 23 million years ago, a comet or asteroid about 2 kilometers in diameter slammed into what is now Devon Island in the Canadian Arctic. The impactor struck a 1,700-meter-thick layer of Paleozoic sedimentary rocks, primarily limestone and dolomite, which lay on top of much older Precambrian gneiss. The collision released energy equivalent to 100 million kilotons of TNT, instantly creating a crater 23 kilometers (14 miles) wide. The impact was so powerful that it excavated material from a depth of 1.7 kilometers, bringing ancient basement rock to the surface.
In the moments after the impact, a vast sheet of molten carbonate rock covered the crater floor. Unique geological features formed, including shatter cones, cone-shaped fractures in the rock that point towards the center of the impact, which are is evidence of a meteorite strike. The crater also contains extensive deposits of allochthonous impact breccia, a type of rock made of angular fragments of the original target rock fused together by the heat and pressure of the event. Though the climate was much warmer during the Miocene when the impact occurred, with forests of pine and birch covering the land, today the crater sits in a cold and dry polar desert. This harsh environment has resulted in very little weathering, leaving the crater's structure exceptionally well-preserved.
Earth's best stand-in for Mars
The Haughton impact structure's unique combination of geology and climate makes it an unparalleled analog for Mars. The barren terrain, freezing temperatures, dry conditions, and impact-shattered landscape are strikingly similar to the Martian surface. This has made it the focus of the Haughton-Mars Project (HMP), an international and interdisciplinary research effort that began in 1997. Led by planetary scientist Pascal Lee of the SETI Institute and the Mars Institute, the project uses the crater as a natural laboratory to prepare for future human and robotic exploration of Mars.
At the HMP research station, scientists and engineers test new technologies, develop exploration strategies, and study how humans can effectively work in extreme environments. Astronauts practice extra-vehicular activities (EVAs), simulating the challenges of working in a spacesuit on another world. Teams test prototype rovers, drills, and other equipment designed for planetary exploration. The research also includes studying the terrain itself. Geological features like gullies and channels on Devon Island resemble landforms on Mars, and show scientists the processes, such as the flow of meltwater under ancient ice sheets, that may have shaped Mars. The similarities are so pronounced that scientists working there have nicknamed the area "Mars on Earth."