A fully
automated microchip electrophoresis analyzer could someday be deployed in the
search for life on other worlds. Courtesy: Adapted from Analytical Chemistry
2020, DOI: 10.1021/acs.analchem.0c01628.
Although
Earth is uniquely situated in the solar system to support creatures that call
it home, different forms of life could have once existed, or might still exist,
on other planets. But finding traces of past or current lifeforms on other
worlds is challenging. Now, researchers reporting in ACS’ Analytical Chemistry
have developed a fully automated microchip electrophoresis analyzer that, when
incorporated into a planetary rover, could someday detect organic biosignatures
in extraterrestrial soil.
One
critical piece of evidence for life beyond Earth is the presence of certain
organic molecules. Previous missions to Mars have relied on gas chromatography
coupled to mass spectrometry (GC-MS) to separate and detect compounds. However,
the technique has limitations for the analysis of some molecules, such as organic
acids, especially when water, minerals or salts are also in the sample.
Microchip electrophoresis (ME)-based separations, followed by laser-induced
fluorescence (LIF) detection, would be ideal, but current instruments are only
partially automated, which wouldn’t work for interplanetary missions. Peter
Willis and colleagues wanted to develop a portable, battery-powered ME-LIF
instrument that could accept a sample and perform labeling, separation and
detection of organic molecules, all in a fully automated fashion.
The
researchers made a device that included two microchips — one for processing and
labeling a liquid sample, and the other (the ME chip) for separating compounds
— and an LIF detection system. After optimizing the device, the researchers put
it to the test in a simulated Mars mission in a Chilean desert. The team
coupled the analyzer to a portable subcritical water extractor on a remotely
deployed rover system. The rover drilled into the soil to collect samples,
which were delivered to the extractor. Then, water was added to the soil
samples, and they were heated to extract compounds for analysis. The device
detected parts per billion levels of amino acids in soil from three of four
drilling locations. Importantly, the sensitivity was three orders of magnitude
higher than that reported for GC-MS-based methods. Although more work is needed
to ready the instrument for spaceflight and extraterrestrial conditions, this
research lays the foundation for developing ME-LIF instruments for missions
seeking signs of life beyond Earth, the researchers say.