Aiming High! The Search for Biosignatures on Mars Starts High on Earth

My team and I are heading back to Chile.  Between October 14 and November 12, we’ll be returning to South America to explore extraordinary landscapes and planetary analogs, and, to my delight, we are going back to the Andes.

This time, I am taking the SETI Institute NAI (NASA Astrobiology Institute-funded) team to some of our previous research areas, but also to some new, very exciting ones. During the month-long expedition, we will explore the Atacama, the Altiplano, and the Andes at five different sites between 8,000 and nearly 20,000 ft. There, we will try to decrypt how environmental conditions on early Mars could have affected its habitability, and the formation and preservation of biosignatures.  Most importantly, we will try to understand how we can detect these biosignatures in the geological record during the next mission to Mars. Our work is meant to provide context to the upcoming Mars 2020 mission, help develop exploration strategies, and new detection tools. We are taking with us a number of in situ instruments that are highly relevant to the Mars 2020 and ExoMars scientific payloads. 

The region we will examine has been the focus of astrobiological investigations – and a training ground for planetary exploration technologies – for over two decades now, and that’s not by accident. While the Atacama is known as one of the driest places on Earth, that’s only one aspect of its planetary analogy. As we go higher through a transect that crosses the Atacama, the Altiplano, and the Andes, we complete what we call a space-for-time substitution experiment. Basically, since we do not know how to build a time machine yet, we are asking Mother Nature to provide it to us, and she obliges.

The Atacama Desert gives us insights into an extremely dry, barren Mars, at the transition of the Noachian/Hesperian eras, when the atmosphere was pretty much already gone and lakes were only salty scars left on the landscape. There, we learn about the last stand for surface life on Mars and how deteriorating surface conditions could have affected the preservation of its record.

The Altiplano, which is on average around 13,000 ft (4,000 m) high, brings us to a younger Mars. It is wetter and sustains lakes that are currently evaporating very fast due to climate change. The landscape is made of volcanoes, hydrothermal springs, and dying lakes with fascinating mineralogical transitions reminiscent of those found on Mars. The atmosphere is thinner as well. This is immediately visible in the morphology and dynamics of the trains of dust devils that form and roam the highlands between 10:00 am and 3:00 pm. I observed the same ones (and at the same time of day, too) 150 million kilometers away from there a few years back in Gusev crater on Mars. In the Altiplano, we learn about a planet in transition and the fight for life survival through adaptation strategies.

Around 20,000 ft, the altitude of our last site, the atmosphere reaches 480 millibars, less than half that of sea level. The daily temperature swing is equivalent to that of Mars at the equator today, and the geology and mineralogy are very similar. There, a few years ago, we measured what remains today the highest levels of UV radiation known in the world.

Why is this important? Lakes at the summit of the high volcanoes harbor life. They are shallow and many are very transparent, which means the UV goes right through. In those lakes, life manages to survive through the development of remarkable strategies, including genetic mutations, pigments (see the photo), and other tricks. Through their study, which will include in situ measurements, sampling, and lab analysis, we may collect precious clues about what, where, and how to search for biosignatures on Mars.

simba summitSummit of the Simba volcano 5,900 m (19,400 ft) – The summit crater lake is shallow and its water column completely transparent (see the shore). The red color of the lake is from an algae that has developed special pigments in response to extreme levels of short wavelength (UVA and UVB) radiation. Credit: SETI Institute/ NAI High Lakes Project

We will be leaving soon now. If you want to follow us, visit SETI Institute social media and its website throughout the duration of the expedition. If you want to learn more about our project and the various institutions involved, visit this page:

-- Nathalie A. Cabrol, Director, Carl Sagan Center