[meteorite-list] A New Test for Life on Other Planets

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?feature=6727

A New Test for Life on Other Planets
Jet Propulsion Laboratory
January 26, 2017

A simple chemistry method could vastly enhance how scientists search for 
signs of life on other planets.

The test uses a liquid-based technique known as capillary electrophoresis 
to separate a mixture of organic molecules into its components. It was 
designed specifically to analyze for amino acids, the structural building 
blocks of all life on Earth. The method is 10,000 times more sensitive 
than current methods employed by spacecraft like NASA's Mars Curiosity 
rover, according to a new study published in Analytical Chemistry. The 
study was carried out by researchers from NASA's Jet Propulsion Laboratory, 
Pasadena, California.

One of the key advantages of the authors' new way of using capillary electrophoresis 
is that the process is relatively simple and easy to automate for liquid 
samples expected on ocean world missions: it involves combining a liquid 
sample with a liquid reagent, followed by chemical analysis under conditions 
determined by the team. By shining a laser across the mixture -- a process 
known as laser-induced fluorescence detection -- specific molecules can 
be observed moving at different speeds. They get separated based on how 
quickly they respond to electric fields.

While capillary electrophoresis has been around since the early 1980s, 
this is the first time it has been tailored specifically to detect extraterrestrial 
life on an ocean world, said lead author Jessica Creamer, a postdoctoral 
scholar at JPL.

"Our method improves on previous attempts by increasing the number of 
amino acids that can be detected in a single run," Creamer said. "Additionally, 
it allows us to detect these amino acids at very low concentrations, even 
in highly salty samples, with a very simple 'mix and analyze' process."

The researchers used the technique to analyze amino acids present in the 
salt-rich waters of Mono Lake in California. The lake's exceptionally 
high alkaline content makes it a challenging habitat for life, and an 
excellent stand-in for salty waters believed to be on Mars, or the ocean 
worlds of Saturn's moon Enceladus and Jupiter's moon Europa.

The researchers were able to simultaneously analyze 17 different amino 
acids, which they are calling "the Signature 17 standard." These amino 
acids were chosen for study because they are the most commonly found on 
Earth or elsewhere.

"Using our method, we are able to tell the difference between amino acids 
that come from non-living sources like meteorites versus amino acids that 
come from living organisms," said the project's principal investigator, 
Peter Willis of JPL.

Key to detecting amino acids related to life is an aspect known as "chirality." 
Chiral molecules such as amino acids come in two forms that are mirror 
images of one another. Although amino acids from non-living sources contain 
approximately equal amounts of the "left" and "right"-handed forms, amino 
acids from living organisms on Earth are almost exclusively the "left-handed" 
form.

It is expected that amino acid life elsewhere would also need to "choose" 
one of the two forms in order to create the structures of life. For this 
reason, chirality of amino acids is considered one of the most powerful 
signatures of life.

"One of NASA's highest-level objectives is the search for life in the 
universe," Willis said. "Our best chance of finding life is by using powerful 
liquid-based analyses like this one on ocean worlds."

Caltech in Pasadena, California, manages JPL for NASA.

News Media Contact
Andrew Good
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-2433
andrew.c.good at jpl.nasa.gov

2017-017