Starry sky view into the space, milky way, bright stars created
π Science and technology
Lasers: promising applications for research and beyond

Detecting life on other planets with lasers

Ricardo Arévalo, Associate Professor at the University of Maryland
On May 31st, 2023 |
4 min reading time
Ricardo Arévalo
Associate Professor at the University of Maryland
Key takeaways
  • A prototype miniaturised instrument could identify organic molecules that could indicate the presence of extra-terrestrial life.
  • The instrument combines the Orbitrap analyser, a spectrometer invented in the 1990s, with laser desorption mass spectrometry (LDMS).
  • This means it can detect larger molecules, where smaller organic compounds are not always signs of life forms.
  • The instrument minimises its mass, volume and energy consumption: it weighs less than 8 kg for just a few centimetres.
  • A precursor for other future instruments, it will considerably enhance future astrobiology and geochemistry missions.

Ricar­do Aré­va­lo and his col­leagues have devel­oped a pro­to­type minia­turised instru­ment that could detect and iden­ti­fy com­plex organ­ic mol­e­cules that could indi­cate the pres­ence of life on oth­er plan­ets and moons in our Solar Sys­tem. Their ‘Orbi­trap-Laser Des­orp­tion Mass Spec­trom­e­try’ instru­ment is a frac­tion of the size and weight of its pre­de­ces­sors and could be used on future space explo­ration mis­sions such as NASA’s Artemis pro­gramme and the Ence­ladus Orbilander.

The search for life else­where in our Solar Sys­tem is a major sub­ject of study. Sev­er­al mis­sions are planned for the com­ing decades, for exam­ple to explore plan­e­tary bod­ies such as Ence­ladus (a moon of Sat­urn) and Europa (a satel­lite of Jupiter). These moons have large under­ground reser­voirs of water that could poten­tial­ly har­bour forms of life. For mis­sions tar­get­ing these plan­e­tary bod­ies, it will not only be impor­tant to be able to detect sim­ple organ­ic mol­e­cules, but also to recog­nise a vari­ety of bio­mark­ers, such as pro­teins and com­plex biostruc­tures. These can be pro­duced by dif­fer­ent types of micro-organisms.

Combining laser and spectrometer

Minia­turised mass spec­trom­e­ters for plan­e­tary explo­ration are not new, dat­ing back to the 1970s with the Apol­lo 15 mis­sion. In the con­text of life detec­tion and astro­bi­ol­o­gy, these instru­ments have been used to detect and iden­ti­fy volatile organ­ic sub­stances from beneath the sur­face of Mars, in the plumes of Ence­ladus and in the atmos­phere of Titan. How­ev­er, to date, no deployed mass spec­trom­e­ter has analysed com­plex non-volatile organ­ic mol­e­cules such as pep­tides and proteins.

Larg­er, more com­plex mol­e­cules are more like­ly to have been cre­at­ed by liv­ing systems.

Laser Des­orp­tion Mass Spec­trom­e­try (LDMS) could be just the thing. This tech­nique uses a focused ultra­vi­o­let laser beam to des­orb and ionise organ­ic mol­e­cules, enabling their chem­i­cal com­po­si­tion to be deter­mined on the basis of their mass-to-charge ratio. The advan­tage of this tech­nique? The laser light can be focused on a small spot on the sam­ple sur­face, allow­ing grains, dust par­ti­cles and oth­er micron-scale struc­tures to be accu­rate­ly char­ac­terised, and ‘chem­i­cal maps’ can be col­lect­ed by scan­ning the laser beam across the sam­ple sur­face. The LDMS also min­imis­es con­tact between the instru­ment and the sam­ple, reduc­ing the risk of sam­ple con­t­a­m­i­na­tion – a sig­nif­i­cant prob­lem in astrobiology.

Ricar­do Aré­va­lo and his col­leagues’ new instru­ment com­bines LDMS with an Orbi­trap analyser, a mass spec­trom­e­ter invent­ed in the 1990s by team mem­ber Alexan­der Makarov (who now works at Ther­mo Fish­er Sci­en­tif­ic in Ger­many). Dur­ing oper­a­tion of the instru­ment, ions des­orbed from the sam­ple are direct­ed towards this analyser, which then traps them in orbits around an elec­trode. The move­ments of the ions can be tracked and this infor­ma­tion analysed to deter­mine the mass of the ions. This mass data can then be used to iden­ti­fy the mol­e­c­u­lar for­mu­lae of the organ­ic com­po­nents in the sample.

Detecting more complex organic molecules 

“Our instru­ment inte­grates a pulsed UV laser sys­tem that effi­cient­ly ‘zaps’ mate­ri­als and an analyser that sep­a­rates chem­i­cal species from the sam­ple accord­ing to their respec­tive mass­es,” explains Ricar­do Aré­va­lo. Togeth­er, these two sub­sys­tems enable the detec­tion and, more impor­tant­ly, the unam­bigu­ous iden­ti­fi­ca­tion of larg­er and more com­plex organ­ic mol­e­cules, which are more like­ly to be of bio­log­i­cal ori­gin. “It’s impor­tant to be able to detect larg­er mol­e­cules,” he explains, “because small­er organ­ic com­pounds such as amino acids, for exam­ple, are more equiv­o­cal sig­na­tures of life forms.”

“Amino acids can be pro­duced abi­ot­i­cal­ly, which means that they are not nec­es­sar­i­ly evi­dence of life,” Ricar­do Aré­va­lo details. “Mete­orites, many of which are filled with these mol­e­cules, can crash onto the sur­face of a plan­et or moon and bring organ­ic sub­stances with them. We now know that larg­er, more com­plex mol­e­cules, such as pro­teins, are more like­ly to have been cre­at­ed by, or to be asso­ci­at­ed with, liv­ing systems.”

The new instru­ment com­bines LDMS and Orbi­trap, two well-estab­lished tech­nolo­gies, to min­imise mass, vol­ume and ener­gy con­sump­tion. The instru­ment weighs less than 8 kg (com­pared with around 180 kg for lab­o­ra­to­ry equiv­a­lents) and mea­sures just a few cen­time­tres. How­ev­er, it has the same ultra-high mass res­o­lu­tion capa­bil­i­ty as larg­er com­mer­cial sys­tems and can detect biosig­na­tures of mol­e­cules at con­cen­tra­tions that would be expect­ed in the sub­sur­face of Europa and Enceladus.

Improving astrobiology

Ricar­do Aré­va­lo hopes to send the device into space in the next few years and deploy it on a plan­e­tary tar­get. He sees the pro­to­type as a “pre­cur­sor” for oth­er future instru­ments based on LDMS and Orbi­trap and believes it has the poten­tial to sig­nif­i­cant­ly improve the way in which the geo­chem­istry or astro­bi­ol­o­gy of a plan­e­tary sur­face is studied.

“Our instru­ment pro­vides access to a wide range of phys­i­cal and chem­i­cal sig­na­tures reflect­ing life, includ­ing strat­i­fi­ca­tions rep­re­sent­ing fos­silised micro­bial com­mu­ni­ties; min­er­als pro­duced by bio­log­i­cal com­pounds; organ­ic com­pounds such as pro­teins, nucleotides [com­po­nents of DNA] and lipids [con­stituents of cell membranes].”

Our instru­ment pro­vides access to a wide range of phys­i­cal and chem­i­cal sig­na­tures reflect­ing life.

“The com­ple­tion of this laser mass analyser demon­strates the matu­ri­ty of the instru­ment and shows that the tech­nol­o­gy is ready to explore extrater­res­tri­al plan­e­tary envi­ron­ments. It is small, ener­gy-effi­cient and robust enough to be deployed in envi­ron­ments such as Ence­ladus and Europa to search for signs of extrater­res­tri­al life. Its devel­op­ment has involved years of inter­na­tion­al col­lab­o­ra­tion with our part­ners at the Lab­o­ra­toire de Physique et Chimie de l’En­vi­ron­nement et de l’E­space in Orléans, France, and Ther­mo Fish­er Sci­en­tif­ic in Ger­many, and I am par­tic­u­lar­ly proud of the num­ber of ear­ly career researchers who have con­tributed so cen­tral­ly to this study.”

The next step for his team is to under­stand how the new instru­ment can com­ple­ment the capa­bil­i­ties of oth­er state-of-the-art instru­ments, such as those cur­rent­ly oper­at­ing on the sur­face of Mars. « This will help us to design the most com­plete and com­pelling pay­load suite for future astro­bi­ol­o­gy mis­sions, » says Ricar­do Arévalo.

Isabelle Dumé



Our world explained with science. Every week, in your inbox.

Get the newsletter