Sciency Words: Sinkers, Floaters, and Hunters

Sciency Words: (proper noun) a special series here on Planet Pailly focusing on the definitions and etymologies of science or science-related terms.  Today’s Sciency Word is:

SINKERS, FLOATERS, and HUNTERS

In the 1970’s, Carl Sagan and fellow astrophysicist Edwin Salpeter were curious about the orangey-red coloration seen on certain parts of Jupiter.  That sort of orangey-red color is frequently associated with organic chemistry (see my post on tholin).

So in this 1976 technical report for NASA, Sagan and Salpeter hypothesize that we really are seeing organic compounds in Jupiter’s atmosphere.  They then go on to imagine what kind of life might develop on a planet like Jupiter.  As a frame of reference, they start by describing one specific example of life here on Earth:

The best analogy seems to be the surface of the sea.  Oceanic phytoplankton inhabit a euphotic zone near the ocean surface where photosynthesis is possible.  They are slightly denser than seawater and passively sink out of the euphotic zone and die.  But such organisms reproduce as they sink, return some daughter cells to the euphotic zone through turbulent mixing, and in this way maintain a steady state population.

So if microorganisms exist on Jupiter, perhaps they follow a similar lifecycle.

Sagan and Salpeter name these hypothetical microorganisms “sinkers,” since sinking is pretty much the defining characteristic of their lifecycles.  But if these sinkers really do exist, then Jupiter may be able to support other, more complex forms of life as well.

Sagan and Salpeter go on to describe “floaters.” Floaters would be giant organisms, perhaps several kilometers in radius.  In order to remain buoyant, they’d have to have very thin skin and be filled with a lifting gas like hydrogen.  Floaters would drift aimlessly through the skies of Jupiter, feeding on the rising and falling swarms of sinkers.

And then there would be “hunters,” as Sagan and Salpeter call them, though that term may be misleading.  Hunters would be able to maneuver deliberately through the air, “hunting” for other organisms.  But these hunters would not eat their prey, at least not in the way we understand eating.  Instead, through a process called “coalescence,” the hunter and the hunted would merge together as one giant super-organism.

Personally, I think Sagan and Salpeter let their imaginations run a little too wild in this paper.  Could life exist on Jupiter?  Sure.  The universe is full of possibilities.  Can we predict with any specificity what life on Jupiter would be like?  I doubt it.

Still, the Jovian ecosystem that Sagan and Salpeter described seems plausible enough.  For the purposes of science fiction, it deserves some attention, and it inspired the short story I posted on Monday.  However, if you haven’t read that story yet, I have to confess (spoiler warning): it turns out the planet in that story is not Jupiter.