Categories: Astrobiology

Researchers Develop a new Framework for Searching for Biosignatures

Planning ahead is something astronomy and space exploration excels at.  Decadal surveys and years of engineering effort for missions give the field a much longer time horizon than many others.  In the near future, scientists know there will be plenty of opportunities to search for biosignatures everywhere from nearby ocean worlds (i.e. Titan) to far away potentially habitable exoplanets.  But it’s not clear what those biosignatures would look like.  After all, currently there is only Earth’s biosphere to study, and it would be unfortunate to miss hints of another just because it didn’t look like those found on Earth.   Now a team led by researchers at the Santa Fe Institute (SFI) have come up with a framework that could help scientists look for biosignatures that might be completely different from those found on Earth.

That framework relies on stoichiometry. A common feature of high school chemistry classes, stoichiometry is the study of chemical ratios.  There are some obvious stoichiometric ratios on Earth that are clearly formed by life as we know it. Generalizing those ratios to be applicable anywhere was the focus of the paper from SFI.  There were three main principles that collectively make up the new framework.  

UT video discussing biosignatures.

The first principle is that stoichiometric values change with the cell size of individual cells.  For example, as bacteria grow bigger the concentration of RNA increases while the concentration of individual proteins decreases.  When those cells die, their size would help to determine what concentration of molecules are released into the environment.

Environmental distribution is also impacted by the second principle – that the number of cells in an environment follows a power law distribution in relation to their size.  For example, there are most likely many more small cells than there are large ones, according to the simplest power law distribution curve.  This size ratio, along with the stoichiometries associated with those different sizes then led to the third principle.

Example of a power law distribution. Lower values on the x-axis (sizes of particles in this case) lead to large quantities (y-axis).
Credit – Hay Kranen / PD / Wikipedia

Applying that stoichiometric principle one step further leads to a result that can be applied to biospheres more generally.   In this case, the size of a given particle is a determining factor of its ratio with the fluid that it is surrounded by.

Let’s continue using RNA and proteins as an example. RNA is an order of magnitude bigger than a protein.  It is also more prevalent in larger cells, according to the first principle.  Larger cells, however, are less prevalent in the environment, according to the second principle.  Therefore, in a biologically active system, proteins, which are smaller, are more likely to have a higher concentration in a surrounding fluid than RNA, which is larger, would.  Hence, the third principle that its size determines a particle’s concentration in a surrounding liquid.

UT video discussing the possibility of life on Titan.

The immediate application of this framework is studying ocean worlds, like Titan or Enceladus, where there are likely liquid bodies that could have concentrations of biological molecules inside of them.  Unfortunately, for now, there are no systems that can accurately measure particle size that could launch on any missions to these worlds.  But that doesn’t mean there won’t be in the future. So the potential for using this framework now requires a bit more engineering expertise to develop such a system.  And it’s already clear how good the astronomy and space exploration community are at that.

Learn More:
SFI – Origins of life researchers develop a new ecological biosignature
Journal of Mathematical Biology – Generalized Stoichiometry and Biogeochemistry for Astrobiological Applications
Astrobiology – Exoplanet Biosignatures: A Framework for Their Assessment
UT – What’ll It Take to Find Life? Searching the Universe for Biosignatures

Lead Image:
Artist conception of life on another planet
Credit: NASA

Andy Tomaswick

Recent Posts

NASA is Building a Nuclear Reactor to Power Lunar and Martian Exploration!

NASA and the U.S. Dept. of Energy have come together to solicit design proposals for…

21 hours ago

InSight Peers Deep Below the Surface on Mars

The InSight lander has been on Mars, gathering data for a thousand days now, working…

2 days ago

Astronauts Took A Fly-around of the International Space Station. Here are Their Stunning Pictures

When astronauts left the International Space Station in early November to return home on the…

2 days ago

NASA Simulation Shows What Happens When Stars Get Too Close to Black Holes

What happens to a star when it strays too close to a monster black hole?…

3 days ago

The Parker Solar Probe is getting pelted by hypervelocity dust. Could they damage spacecraft?

There’s a pretty significant disadvantage to going really fast - if you get hit with…

3 days ago

The Decadal Survey is out! What new Missions and Telescopes are in the Works?

It’s that time again.  Once every ten years, the American astronomy community joins forces through…

3 days ago