After nearly two decades orbiting the Red Planet, NASA’s Mars Reconnaissance Orbiter (MRO) is performing ambitious new maneuvers — essentially, backward flips — to boost its radar’s ability to search for crucial subsurface water ice, a key to Mars’ past and future exploration. This innovative approach allows the spacecraft to probe deeper than ever before, potentially revealing vital ice deposits hidden up to 1.2 miles (2 kilometers) below the Martian surface.
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An Aging Orbiter Gets a New Lease on Life
Launched in 2005 and arriving at Mars in 2006, the Mars Reconnaissance Orbiter is a veteran explorer. It carries several powerful instruments, like the super-sharp HiRISE camera, that have revolutionized our understanding of the Martian surface. To point these instruments, MRO typically tilts or “rolls” by a small amount, up to 28 degrees. While effective for most observations, this standard tilt wasn’t ideal for one specific instrument: the Shallow Radar, or SHARAD.
The SHARAD Challenge: A Blocked View
The SHARAD instrument is designed to send radar pulses down into Mars and listen for echoes that can reveal layers of rock, dust, and potentially, water ice buried underground. Think of it like using sonar on Earth to map the seafloor. However, SHARAD is located on the rear of the spacecraft. When MRO performs its standard tilts, parts of the spacecraft itself often get in the way, partially blocking SHARAD’s view and weakening its signal. This interference limited how deep SHARAD could see, leaving some potentially ice-rich regions just out of reach.
Artist's impression of the Mars Reconnaissance Orbiter flying above the surface of Mars.
Scientists knew there was value in exploring these deeper areas. Gareth Morgan, a co-investigator on the SHARAD team, noted that the instrument was designed for the near-subsurface, but they could gain a lot by getting a closer look at those slightly deeper regions.
The “Very Large Roll”: Flipping for a Better Signal
To overcome this limitation, MRO engineers decided to try something new starting in 2023. Instead of a small tilt, they experimented with “very large rolls” — rotating the spacecraft by a dramatic 120 degrees. This maneuver essentially spins MRO almost upside down relative to the Martian surface.
During this extreme roll, the SHARAD instrument gains an unobstructed view. The radar signal, no longer blocked by the spacecraft’s structure, becomes up to 10 times stronger. This allows the radar waves to penetrate deeper and detect fainter echoes from potential water ice layers buried further down.
The Catch: Power and Communication
Performing such a large roll is a complex operation. During a small tilt, MRO’s large communication antenna can stay pointed at Earth, and its solar panels can track the Sun to maintain power. A 120-degree roll breaks these connections. The antenna loses sight of Earth, and the solar panels can’t efficiently collect sunlight.
Animation showing the Mars Reconnaissance Orbiter performing a large roll maneuver in space, rotating its body.
This means a very large roll requires careful planning to ensure the spacecraft has enough battery power to complete the maneuver safely and resume normal operations. Currently, the MRO team is limiting these ambitious rolls to just one or two times per year, though they hope to streamline the process in the future to potentially increase the frequency.
Why Finding Water Ice Matters So Much
Discovering large, accessible deposits of water ice near the surface is crucial for future human missions to Mars. Astronauts could use this ice not only for drinking water but also to produce oxygen for breathing and rocket fuel for returning to Earth.
Beyond supporting future explorers, the presence of water ice at different locations and depths is a window into Mars’ ancient past. It can reveal more about the planet’s climate history and how water, a key ingredient for life as we know it, behaved on Mars over billions of years.
A Bonus for Another Instrument
The large rolls offer an unexpected benefit for another MRO instrument: the Mars Climate Sounder. This instrument studies small changes in temperature and atmospheric layers. It used to rely on its own dedicated pointing mechanism, but that system has become unreliable with age. Now, the Climate Sounder depends on MRO’s body movements for pointing. The very large 120-degree rolls give the Climate Sounder more flexibility and opportunities for its observations.
Detailed illustration depicting the Mars Reconnaissance Orbiter spacecraft orbiting the red planet, Mars.
These new maneuvers demonstrate the ingenuity of the MRO team and show that this aging spacecraft is still capable of groundbreaking science. By learning to perform these impressive ‘flips’, MRO continues its mission to unlock the secrets hidden beneath the surface of Mars, paving the way for future exploration and deepening our understanding of the Red Planet’s watery past. The initial success of these large rolls has been detailed in The Planetary Science Journal.
