NASA's Curiosity Rover and Perseverance Rover are investigating whether ancient life once existed on Mars. The evidence we are looking for may be buried deeper than we previously thought.

Any evidence of leftover amino acids from that time, if there was life on Mars, would have had to be buried at least 6.6 feet below ground level and buried at least 6.6 feet deep. 

Due to its weak atmosphere and lack of a magnetic field, Mars' surface experiences much more cosmic radiation than Earth's. And cosmic radiation destroys amino acids.

NASA's Goddard Space Flight Center's Alexander Pavlov says the amount of cosmic radiation, amino acids, and minerals on Mars' surface has been underestimated. Destroys much faster than is expected.

Mars exploration is complicated by cosmic radiation. Cosmic radiation exposes humans to 0,33 millisieverts a year. This is more than 250 millisieverts on Mars.

Researchers Pavlov and his team aimed to understand better whether amino acids were found on the surface of Mars in their study published in Astrobiology. They conducted experiments.

After that, the test tubes were sealed. Each test tube portrays a different temperature of the atmosphere on Mars. Radiation was then applied to him. By destroying the amino acids, the simulant soil was created.

The results showed that silicates, especially silicates with perchlorates, increased the rate of amino acid degradation. 

There are no amino acids on the surface of Mars that are older than 100 million years, which means that they have all been destroyed.

Thus, on Mars, amino acids must be found a little deeper than the surface. About 6.6 feet below the surface. Mars rover's drilling capabilities are limited to two inches.