VIPER: Mapping water ice on the Moon
- Mission status: cancelled
Rovers act like scientists' eyes and hands – they help analyze samples of rock, soil and volatiles on location, and send data back to Earth. Using their tools and instruments, they can help scientists learn more about important resources on the Moon that will be needed to establish a long-term presence on the Moon and send humans farther into space.
NASA's Volatiles Investigating Polar Exploration Rover (VIPER) was going to map water ice near the Nobile Crater at the south pole of the Moon. It would have been the first resource mapping mission on another celestial body. The solar-powered golf cart-sized rover was intended to use several science instruments and a 1-metre drill to collect samples in precise locations selected by experts and analyze them on site.
This mosaic image of the south polar region of the Moon is made up of more than 1500 images taken by the Clementine spacecraft. The region around the Nobile Crater is where VIPER would have roamed. Nobile crater is circled. Since the Moon's axis is nearly perpendicular to the Sun, sunlight does not reach the bottom of craters at the poles. The Moon's south pole therefore contains many areas that are permanently shadowed – making it an attractive target for water-seeking exploration. (Credit: NASA/JPL/USGS/Canadian Space Agency)
What are lunar volatiles?
Volatiles are chemical elements or compounds that can be easily vaporized. Some examples of volatiles are hydrogen, water, helium, and carbon dioxide. When heated, these substances can be released as a gas, making them difficult to handle. However, lunar volatiles are likely to play a key role in the sustainable presence of humans on the Moon because they could be used as a fuel source, to create breathable air, or as a source of water.
Volatiles within the lunar regolith (the soil present on the surface of the Moon) can have different origins:
- Chemically trapped when the Moon was originally formed;
- Delivered by the solar wind, or the impact of a comet or meteorite; or
- Redistributed from different areas on the Moon.
An artist's concept of VIPER on the lunar surface. Equipped with headlights, VIPER would have helped determine the distribution of ice water on the surface and subsurface down to depths of one metre. (Credit: NASA Ames/Daniel Rutter)
Objectives
The objectives of the VIPER mission were to:
- Map the location of ice deposits
- Sample soils to determine water ice distribution
- Learn more about the origin of water on the Moon
- Prepare for deep-space human exploration
Challenges of designing a lunar rover
Creating a rover that can survive on the Moon is no easy task. Engineers had to uniquely adapt VIPER to be able to survive and work in high-contrast lighting conditions, extreme temperature ranges, diverse soil types, and steep crater walls. The rover also would have needed to be able to communicate with Earth.
- Extreme contrasts in light
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High-contrast lighting differences between the sunlit and shadowed areas on the Moon would have posed a unique challenge. On Earth, particles in the air reflect and scatter sunlight so shadows are not fully dark, but dimly lit with indirect light. On the airless lunar surface, there are no particles to reflect and scatter sunlight – leading to regions exposed to very bright sunlight, and extremely dark areas. Shadows at the south pole are long and fast-moving due to the low angle of the Sun on the horizon. The low angle of the Sun combined with some topographical features can result in some areas never being exposed to the Sun; these are called permanently shadowed areas. These lighting issues can affect a rover's depth perception and ability to detect hazards.
- Intense temperatures
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Equipped with headlights, VIPER would have been able to explore the pole's permanently shadowed craters. The Moon's lighting conditions demand the use of a specialized lighting and camera system. And the contrast doesn't stop at lighting – the change from sunlight to shade also means extreme temperature changes. The temperature difference between shaded and sunlit areas can range from −248 to 123 degrees Celsius.
The permanently shadowed craters near the lunar south pole are some of the coldest locations in the solar system, where it is suspected that ice has been stored for billions of years. Since the water has remained frozen for a very long time, mission scientists would have been able to investigate where the water on the Moon came from and how much water exists there. Since the rover was solar-powered, VIPER would have had to recharge its batteries in the Sun and use its heaters to remain warm enough to travel to sampling locations in the shaded craters.
- Route planning
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To conserve energy, VIPER would have needed to be able to move to a "safe haven" and go into hibernation. Places with shorter nights are called safe havens. For VIPER, a place where slivers of sunlight can reach the rover's solar panels would have been important to keep its batteries charged. Getting VIPER to a safe haven would have been vital to keep its internal components warm.
- Mobility
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The rover's wheels would have needed a lot of agility to be able to drive on a variety of soils and navigate the craters. VIPER was able to drive sideways, diagonally or even spin its wheels in a circle and drive backwards without changing what direction it is facing. In case the rover had encountered soft soil, VIPER was able to even operate each wheel separately. The all-metal wheels was able tackle slopes with inclines of up to 30 degrees.
Credit: NASA/GRC/Bridget Caswell
Credit: NASA/GRC/Jef Janis
Rover wheels and prototypes must undergo lots of testing. Pictured here at the Simulated Lunar Operations Laboratory within NASA Glenn Research Center, the all-metal wheels traverse steep slopes, soft material, and rocks.
- Communicating with the rover
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Direct line-of-sight radio communications with Earth would have allowed the team to operate interactively in near real time. The communications would have been sent over the Deep Space Network. The delay would have been only be 6 to 10 seconds compared to 10 to 20 minutes when sending commands to Mars. This would have allowed rover drivers to make decisions quickly based on obstacles the rover encounters.
From to , six Apollo missions brought back 382 kilograms of rocks, sand, dust and core samples from the Moon. As part of the Soviet Union's Luna program, three missions returned 300 grams of lunar samples to Earth in , and .
Studies of lunar rocks give information about the origin of the Moon, the formation of the Moon's crust, and a history of solar activity. Orbiter and impact missions showed the presence of some water ice.
VIPER was aiming to travel up to 20 kilometres to directly sample frozen water at different depths and temperatures. Its mission would have helped scientists identify the distribution, origins, and permanence of frozen water on the Moon.
Canada's role in the mission
Dr. Myriam Lemelin, professor of applied geomatics at the University of Sherbrooke. (Credit: Université de Sherbrooke)
The Canadian Space Agency is providing funding to the University of Sherbrooke to support the participation of Dr. Myriam Lemelin, professor of applied geomatics, in her role as a member of the mission science team.
Dr. Lemelin was selected by NASA as one of the experts who will enhance the scientific value of the samples to be analyzed by remote sensing instruments on the rover: the Near InfraRed Volatiles Spectrometer System (NIRVSS) and the Ames Imaging Module (AIM). Dr. Lemelin will contribute her expertise in remote sensing to help learn more about the composition of volatiles, including water ice, and geological processes occurring in the south pole region.