Exploring beneath the surface of other planets may be the key to determining whether life has ever existed outside of Earth.

Recently, the Curiosity rover measured total organic carbon, a necessary ingredient in the molecules of life, in Martian rocks for the first time. But it doesn't prove that life ever existed on Mars, because carbon can also be produced by non-living sources.

New research suggests that the best chance of finding past or present evidence of life on Mars requires going beneath its surface, at least 6.6 feet (2 meters) below. Mars has an incredibly thin atmosphere, meaning the red planet's surface is bombarded by high-energy radiation from space, and that could quickly degrade substances like amino acids that provide fragile evidence of life.

Those harsh surface conditions also present a challenge for astronauts, which is why scientists have suggested that caves on other planets could hold the key to future exploration. Vast cave systems on the Moon and Mars could act as shelters for future space travelers.

Caves could also contain resources such as water, reveal more about a planet's history, and be havens for evidence of microbial life. On Earth, there is a diverse range of cave systems, many of which remain unexplored, and host diverse groups of microorganisms.

Before humans land on Mars and explore its subsurface, a group of scientists wants to send ReachBot, a robot designed to crawl and climb through extraterrestrial caves.

The idea for ReachBot was born in 2018 when Marco Pavone, director of Stanford University's Autonomous Systems Laboratory, and his students brainstormed concepts for a Martian cave explorer.

One of his students suggested the idea of ​​a small robot with extendable arms that extend like a tape measure, which could be used in the same way Spider-Man shoots webs to help him navigate the New York City skyline. .

The robot concept is the size of a basketball and a toaster oven and is covered with extendable arms equipped with spiny pincers that could grasp objects and grab or push off the steep, rocky surfaces of Martian caves. It would be able to anchor and crawl long distances.

Pavone, who is also an associate professor of aeronautics and astronautics at Stanford University's School of Engineering, and his students came up with the idea of ​​a robot with extendable arms. They created a proposal to submit to NASA's Innovative Advanced Concepts Program, which funds visionary concepts in the field of space robotics that could transform future missions.

The team will use the next two years to work on 3D simulations, a robot prototype, develop strategies that help the robot avoid risks, and test ReachBot in a realistic mission environment. These tests will determine how ReachBot could be used for future explorations.

• Exploring beneath Mars

If ReachBot becomes its own mission, it will likely rely on a larger, more capable robot, such as a rover, to access the caves it will explore. The rover will take ReachBot to the cave entrance or leave it on a cliff face, which ReachBot could climb.

ReachBot is likely equipped with cameras, microscopes, and a remote sensing method called LIDAR. But the instruments require power and add weight, in addition to the power and communication system the robot will need.

The team envisions that ReachBot will be connected to the surface-bound rover, which can provide power and act as a communications relay, said Stephanie Newdick, a doctoral student in aeronautics and astronautics at Stanford University's School of Engineering.

In addition to sending data to the rover, ReachBot may also have a conveyor belt system that allows it to collect samples and send them to the surface. ReachBot can also be useful in environments such as the International Space Station or the Gateway.

The ends of ReachBot's arms could also be equipped with scientific instruments that can get into small cracks and crevices where a robot wouldn't fit. A creation on as a way to further explore the solar system, going to places where humans cannot yet set foot.