Scientists suspect Mars was once habitable, but radiation and oxidants erase biological traces. New tests exposing DNA on stones to simulated Martian radiation show that full sequences degrade, yet fragments can survive long enough for taxonomic identification, aiding the search for past life.

By Sean Tsoi

Are we alone in space?

From believing Earth was the centre of the universe over 400 years ago, to discovering our planet is just 1 of 100 billion - 1 trillion planets in the Milky Way Galaxy, our understanding of space has developed significantly. Though this vast number is true, we are still yet to find evidence of another life-inhabiting planet. This was until researchers at the Centro de Astrobiología (CAB) in Madrid, Spain, developed a strategy to detect traces of DNA on Martian rocks, potentially bringing the search for life much closer to home (Brennan, 2020).

Why Mars?

Given its Earth-like characteristics, Mars stands out as a prominent candidate for potential life in our solar system. It has a solid surface providing a landing space and has less extreme environmental conditions compared to other planets in our solar system, such as Jupiter and Saturn, that are gaseous and extremely hot (European Space Agency, n.d.). This opened the way to the ‘Curiosity’ rover project led by NASA, launched in 2011, aimed to remotely research the physical aspects of Mars.

Through the rover's 13 years of data collection, it collected over 3,279 gigabytes of data, equivalent to more than 1,000 high-definition movies (Holloway et al., 2024). Amongst the data, the most important was the discovery of large amounts of organic carbon on Martian rocks, estimated to date back almost 3,500 million years. Seeing as carbon could survive the radiation on Mars over a prolonged period of time, questions surrounding the presence of other biological molecules on Mars arose, and if more complex compounds exist such as DNA, leading to the investigation by the CAB.

The Investigation

Organic carbon is a chemically stable and persistent molecule that enables it to survive and be easily extracted from Martian rocks. On the other hand, DNA is a much more complex compound, making it fragile and susceptible to degradation by the environment, leaving scientists curious if DNA even has the potential to survive Mars’s radiation.

To explore this, researchers first collected sedimentary Earth rocks with similar total organic carbon content and physical aspects to the Martian rocks found. The rocks were then sealed in a vacuum-tight container and placed in an irradiation facility pool, surrounded by large sources of radioactive Cobalt-60 for 20 days. These specific conditions simulate up to 136 million years of gamma radiation that the rocks would have been exposed to if left on Mars.

Following the 20 days, the rocks were extracted from the radioactive conditions to be examined, and what was found was astonishing. While simpler biological molecules such as lipids and amino acids were quickly degraded, 1.48–8.45% of DNA sequences survived in fragments, leaving sufficient material for taxonomic identification and resequencing (Maria-Paz Zorzano et al., 2025).

What does this mean moving forward?

This discovery by CAB, that DNA fragments can survive years of radioactive exposure, advances our understanding and potential to detect life on Mars and other planets with similar conditions.

DNA is considered the molecule of life, as it carries the genetic information that shapes the development, growth and overall being of all living organisms. It is a hereditary material, meaning that it is passed down during reproduction to offspring. This essentially makes DNA a book that can be sequenced and analysed to explain the identity of its corresponding organism.

Therefore, by being able to detect DNA on Mars, we can learn all about what living organisms may have once lived on Mars, and compare their DNA to DNA of living organisms on Earth in order to determine similarities and potential relationships amongst species, leading to the discovery of the first extraterrestrial species (Nature Education, 2014).

This paves the way for future missions with the intent to uncover and characterise extraterrestrial life, bringing us one step closer to answering the question, are we alone in space?

Reference list

Brennan, P. (2020). Among Trillions of Planets, Are We ‘Home Alone?’ - NASA Science. [online] Nasa.gov. Available at: https://science.nasa.gov/universe/exoplanets/among-trillions-of-planets-are-we-home-alone/.

European Space Agency (n.d.). Why go to Mars? [online] Esa.int. Available at: https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/Why_go_to_Mars.

Holloway, A., Adisoetjahya, J., Swieso, S., Cheung, F., Chien, C., Alderete, K., Denison, J. and Vasavada, A. (2024). The Myth of the Data-Constrained Mission: Ten Years of Data Management Onboard the Curiosity Rover. 2024 IEEE Aerospace Conference, [online] pp.1–16. doi:https://doi.org/10.1109/aero58975.2024.10521196.

Maria-Paz Zorzano, Jyothi Basapathi Raghavendra, Carrizo, D., Fuencisla Cañadas, Reyes-Prieto, M., D’Auria, G. and Martin-Torres, J. (2025). Fragmented deoxyribonucleic acid could be extractable from Mars’s surface rocks. Communications Earth & Environment, [online] 6(1). doi:https://doi.org/10.1038/s43247-025-02809-w.

Nature Education (2014). Introduction: What is DNA? | Learn Science at Scitable. [online] Nature.com. Available at: https://www.nature.com/scitable/topicpage/introduction-what-is-dna-6579978/.