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Astrobiology: The Story of our Search for Life in the Universe

Astrobiologists study the origin, evolution, and distribution of life in the universe. This includes identifying evidence left behind by life that once survived on the ancient Earth, and extends to the search for life beyond our planet.

When looking for signs of life on other worlds, what are they looking for?

Things called biosignatures. For example, when you sign a piece of paper, your signature is evidence of your existence. Similarly, biosignatures are anything that can prove that life was once, or is, present in an environment.

If we were very very lucky, we might spot something we know is life with a powerful telescope or receive a "phone call" or radio signal from alien civilizations. Those types of biosignatures would be obvious. But they would only let us identify advanced life.

For most of Earth’s history (billions of years), single-celled life like bacteria and archaea have been around. Humans have only been making radio transmissions for hundreds of years. So we have a better chance of finding life if we look for signs that have been around for very long periods of time.

Patterns in ancient rocks that were created by life are a great example. That can be anything like a dinosaur footprint or structures built by microorganisms, like stromatolites.

Molecules can also be biosignatures, like DNA left behind for detectives to discover. But DNA doesn’t last very long on its own in most environments, so other molecules like lipids (like natural oils, wax, and fat) might be a better choice if you are looking for signatures of life from millions (or billions) of years ago.

Even the balance of gases in a planet’s atmosphere can be a sign of past or present life. On Earth, biology plays a major role in maintaining the delicate composition of gases like nitrogen, oxygen, and carbon dioxide in the air that we breathe.

These are just a few examples of signs astrobiologists look for when searching for life amongst the stars! Research into these biosignatures inform many of our biggest missions, from observatories like the Hubble Space Telescope and the Webb Space Telescope to our Mars Sample Return endeavor.

Want to learn more about the search for life? Check out the latest issue of our comic-book style graphic history novel, Astrobiology: The Story of our Search for Life in the Universe. This new chapter is all about biosignatures.

Explore life in the universe with us by following NASA Astrobiology on Twitter and Facebook.

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Taking advantage of a total lunar eclipse, astronomers using our Hubble Space Telescope have detected ozone in our atmosphere. Why's this important? 🔭 Researchers can now use this new method – and space telescopes – to continue the search for life in our universe. Find out more HERE. 

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Was There Once Life On Mars?  Our Perseverance Rover Aims to Find Out

Our Perseverance mission is set to launch on Thursday, July 30 and could help answer many longstanding astrobiology questions about Mars. The mission will deliver our Perseverance rover to the Martian surface, and this powerful rover is equipped with a multitude of tools to study the planet's environment and to answer questions about whether or not the Red Planet could have had life in the past.

In preparation for launch, our Astrobiology Program is releasing a new update to Issue #2 of the graphic history series, Astrobiology: The Story of our Search for Life in the Universe. This new, fourth edition tells the tale of our exploration of Mars in relation to astrobiology.

The history of our exploration of Mars is full of struggle and triumph. Mars is a dangerous and difficult planet to visit, with frigid temperatures, damaging dust storms, low gravity, and a thin atmosphere. Despite the challenges, NASA missions have opened our eyes to a world that was much more Earth-like in its past, with environments that contained all the necessary conditions for life as we know it.

Issue #2 tells the complete history of our endeavours on Mars, from the Mariner missions to Viking and Pathfinder to Curiosity. In this fourth edition, you’ll find  details on the Perseverance rover and its journey to search for ancient signs and signatures of life that could once and for all tell us whether or not life gained a foothold on the ancient Red Planet.

Perseverance will also drill into Martian rocks and collect samples that will one day be returned to Earth by a future Mars Sample Return mission. The samples will be stored in special containers and carefully 'cached' in a location on Mars where they will be easily accessible for retrieval. These samples will allow astrobiologists to perform detailed experiments that robots are not yet able to undertake remotely.

Visit astrobiology.nasa.gov/graphic-histories/ to download the new edition of Astrobiology: The Story of our Search for Life in the Universe, and read the entire series to explore NASA’s astrobiology journey to understand the origin and evolution of life on Earth, and the potential for life elsewhere in the Universe!

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What is the most exciting thing you hope to learn?

What will scientists do if Perseverance does find signs of life on Mars?