Exploration of Extreme Environments with Currentand Emerging Robot Systems

The discovery of living organisms under extreme environmental conditions of pressure, temperature, and chemical composition on Earth has opened up the possibility of existence and persistence of life in extreme environment pockets across the solar system. These environments range from the many intriguing moons, to the deep atmospheres of Venus and even the giant gas planets, to the small icy worlds of comets and Kuiper Belt Objects (KBOs). Exploring these environments can ascertain the range of conditions that can support life and can also identify planetary processes that are responsible for generating and sustaining habitable worlds. These environments are also time capsules into early formation of the solar system and will provide vital clues of how our early solar system gave way to the current planets and moons. Over the last few decades, numerous missions started with flyby spacecraft, followed by orbiting satellites and missions with orbiter/lander capabilities. Since then, there have been numerous missions that have utilized rovers of ever-increasing size and complexity, equipped with state-of-the-art laboratories on wheels. Although current generations of rovers achieve mobility through wheels, there are fundamental limitations that prevent these rovers from accessing rugged environments, cliffs, canyons, and caves. These rugged environments are often the first places geologist look to observe stratification from geohistorical processes. There is an important need for new robot mobility solutions, like hopping, rolling, crawling, and walking that can access these rugged environments like cliffs, canyons, and caves. These new generations of rovers have some extraordinary capabilities including being able to grip onto rocks like NASA/JPL LEMUR 2, operate in swarms such as MIT’s microbots, or have high-specific energy fuel cell power supply that is approximately 40-fold higher than conventional lithium ion batteries to Stanford/NASA JPL’s Hedgehog which is able to hop and somersault in low-gravity environments such asteroids. All of these mobility options and supporting technologies have been proposed and developed to explore these hard-to-reach unconventional environments. This article provides a review of the robotic systems developed over the past few decades, in addition to new state-of-the-art concepts that are leading contenders for future missions to explore extreme environments on Earth and off-world.