Life on Ganymede
Views of Ganymedean Life
a) Some Plants
b) The "coral reef" - Actually more plants
c) lively scenes with plants and animals (in "Dark Terrain")
d) the face on Ganymede: the face on Mars has nothing on this apparition!

Speculations About Ganymede Life

a) Favorable Factors of Ganymede's Environment
b) Usage of Craters by Vegetation
c) Life underground?: micro-meteorite protection
d) Heat on Ganymede

Ganymede Life Chemistry

a) Tholins on Ganymede and other airless worlds
b) Oxygen

- All images are by the Galileo Spacecraft, courtesy of JPL and NASA, unless otherwise indicated.
- Written by Craig Carmichael, Independent Researcher, 2005-2007

Views of Ganymedean Life

When we think of seeing life on another world, what is it that comes to mind? First, of course, we look for human works. After all, they should be larger than any animal we're likely to see. Then, we look for animals. Carl Sagan took reptiles out into the desert to photograph them from above and study the images, lest there be any chance of missing any life that might be vaguely disclosed in the Mars Viking images.

But all this overlooks the fact that the largest and most visible form of life is vegetation. From above, one sees the forest canopy, not the monkeys leaping between the branches. Not only do plants grow much bigger than the largest animals, but they grow in great profusion, whereas animals are found singly or in small groups, here and there. In retrospect, it is obvious that plant life would be the thing to search for in distant images of random scenes, taken from space. As it is, I would have missed seeing life on Titan were it not for a few Huygens images that showed what appeared to be undersea creatures in the clear methane sea. It took me months to figure out I was looking at plants, which are almost ubiquitous in the Huygens images (what are those?... huge tentacles?... gigantic antlers?... Have they got the altitude wrong? Finally: No... they're huge STEMS with LEAVES!). Even then the forms of plant life on Ganymede only slowly and grudgingly became apparent to me. But once seen and studied, vegetation on Ganymede is evident even if its exact form is often as vague as the gradually thinning ends of ragged leaves and branches. That no one else appears to have noticed it in the decade since the first Galileo flybys I can only assume demonstrates (a) how little study is given to photographs where the visual meaning isn't immediately clear - they can't be quantified and graphed, so they are dismissed as being "poor quality" and discounted as scientific evidence, (b) how much our attention was diverted by Io's spectacular volcanos and volcanic geysers, and by the evident ocean under Europa's ice, on a mission where Ganymede was only one of five worlds being explored at a distance, (c) how our Earthly prejudices about where life can happen, how big it should be and what form it should take, causes us to mistrust our own eyes -- if we thought we were looking at Earth, or perhaps even Mars, and on a smaller scale, we'd have looked more carefully and identified some of the Ganymedean vegetation as being such, and finally (d) the value of color photography. There's little chance I'd be a lone voice saying "HEY LOOK, THERE'S LIFE ON GANYMEDE!" a decade later if a few of the "close up" photos had been in color.

An odd feature of many of these Galileo images is that in the JPL/NASA originals, they are presented at confusing orientations (even upside down) with low levels of contrast and brightness, in which they looked dull and uninteresting. I have increased the contrast and brightness in some images to see better views and to pick out details more readily. And I might easily be wrong, but I don't think any of the images from orbit 29 (color!) were ever presented anywhere besides the Galileo Image Archive. I've now presented one of them, and I also did some tweaking on it.
   Before leveling criticism that my minor image adjustments constitute adulteration so that the images show things that aren't really there, please remember they are minor adjustments, and I'm saying I've done it. (Then at look at the much greater - even grotesque and certainly misleading - contrast magnifications to the Huygens "raw" images made by DISR at LPL/University of Arizona, in some cases around 1000% or more and often with serious loss of image data, yet they don't mention it or explain it and claim the images as presented are the raw images. In the Galileo Image Archive, there are also a few Ganymede "raw" images where the contrast appears to have been magnified, seemingly to the point of some loss of image data, and it likewise doesn't seem to be mentioned.)

Ganymede shows a surprising variety of types of terrain, each with its own patterns of vegetation... or could it in some cases be a surprising variety of vegetation, which actually defines the terrain?


In this clipping from image 552443500r we discover that some confusing patterns of light and dark make better sense if viewed as being plant stems and leaves with shadows. Some of the vegetation is near ground level with little vertical relief, yet other stems and leaves are way up in the "air", casting definite dark shadows on the surface beneath. While there are many plants casting convincing shadows, the most outstanding one is the plant appearing to circle the largest crater, just right of center in the upper portion of the image. That it is not a geological part of the crater rim beneath it seems clear.
I have colorized just some of the vegetation in the image on the right to help make it more apparent. With an image scale of about 16 meters per pixel showing various organized "frond" patterns, it is apparent that these are not simply boulders strewn about the ground as on the moon and Mars, and that plant life on Ganymede attains to similar huge sizes to that of Titan. Low gravity and lack of strong winds would seem to be common elements between growing conditions on Ganymede and Titan.


This mosaic, clipped from PIA02571, is said to be the closest view of "dark terrain" on Ganymede.
Plants on Ganymede appear to show an interesting tendency to circle around crater rims. Of course, if plants follow what would seem like the natural tendency to want to grow upward, they would grow up the side of a crater until they reach the rim, then, there being no higher elevation, would follow the rim.
The "tentacles" (leaves) on the crater rims at first made me think of coral reef creatures and were a tip-off that Ganymede was alive. I saw giant "tongues" (long, thin leaves?) sticking out of holes that appeared to have been dug by something (bright plants covering crater rims, I think.) Viewed as viney plants, the botanic nature of the scene becomes evident.
In about the center of the right hand side (scroll right) we see what looks a bit like a gigantic "footprint". Whatever caused this, it has allowed us to see a cross-section of Ganymedean soil on the far side, and thus to look into the ground. We see definite structures which could be tunnels, veins, or, most likely, plant roots.

Here we seem to see trees or bushes forming curious rows across the landscape. Again a few colorizations may help to point out the nature of the topography which, with the apparent "undercuts" along each cylindrical shaped feature, would seem most unusual for dead geology. It seems likely that the rows are a combination: geological ridges, with vegetation overspreading them (seeking the high ground and sunlight) and providing the bushy appearance. Craters here and there (with bushy rims) demonstrate the geological component of the scene.

On Earth we tend to expect to see trees growing straight up. If there are no trees, we expect to see instead smaller plants: bushes, grasses, flowers and ferns.

On light gravity worlds like Ganymede and Titan, one would expect to see gigantic trees, but instead we also see giant vines crawling through the sea on Titan, and on Ganymede, huge horizontal fronds, as well as more bush- or tree-like vertical structures.

Again and again we seem to see vegetation forming rows of sorts. An interesting question is whether the rows are defined by lanes of underground mineral deposits, or by some other obscure requirement for plant growth. Perhaps with no air to waft seeds or spores over a distance, and likewise no birds or flying insects to carry them, plants which grow along the ground are better able to spread.

Any human works are evidently too small to identify, leaving only The Urantia Book's statement that there is an airless world of non-breathers "in close proximity" to us as evidence for inhabitation for those who wish to believe the statement and to associate it with Ganymede. Only a future Ganymede orbiter or lander can give us substantially better views. (Please, oh please, take a color camera next time!)

6142, 6135 (both 45 m/p)
Vegetation forming vague rows north of 55 degrees N latitude. Galileo flew past over about 30 degrees north latitude, and this set of images image is looking at 55+ degrees north latitude, so we see advantageous perspective views instead of the usual almost straight down scenes.
Ganymede 'hi-rez' image
Close up details at 56 degrees north (359946139, 45 m/p). Various bizarre features are visible. I believe most of the things that aren't geology are some strange and huge sort of botany. Some look like great blobs of gelatin with branches or other projections. But many such "blurry" or "fuzzy" details could instead be the result of looking through the "canopy" or "crown" of plants - looking at a background through branches with leaves that are too distant to distinguish individually.
On the right side just below center is the "Head on Ganymede". (Step aside, "Face on Mars"!)It's about a kilometer wide and appears to be composed of plants similar to others elsewhere in the image, conspiring accidentally to make an illusion. (I would color that and some other parts of the scene quite differently now if I did it again!)

Anyone who thinks my colorizations are stupid is more than welcome to try to figure out what we're looking at for themselves. This is definitely not Mars, where we are pretty sure what most things are. Ganymede is still a mysterious, alien world that deserves much further study, preferably on its own and not as part of a general Jupiter exploration.

The last few images above are from an overlapping mosaic series that covers a swath from 55 to 65 degrees north, at longitudes facing almost directly away from Jupiter, with an east-west resolution of about 45 meters per pixel. Here is the entire mosaic, rendered perhaps for the first time: GanymedeNorth60Mosaic.jpg .


Top: Polyps and barnacles by the Seashore
Bottom: Surfaces of Three Worlds at the same scale

On Rhea, as on Mars and indeed most airless (or nearly so) worlds, one gets the impression of a surface made up of pulverised rock, dust and soil or grit too fine to see individual pieces of from space. On Ganymede, one sees underlying surface contours defined by craters and other geological formations, but the soil is at least partly blanketed by a "thin" layer of "fluffy" material, nicely matching a description of the surface characteristics as deduced by thermal studies. And the large scale, individually distinct objects rising above the surface form patterns, like vegetation in whatever form it takes does wherever growing conditions are good. Compare the small sea polyps and barnacles in the top image with Ganymede, and then with Rhea. Visually, in spite of the immense difference in scale, it is Rhea that is starkly the "odd man out": it is bare ground, while the other two scenes appear to be covered with life.

Owing to the mechanics of Galileo's camera, close up color images of planetary surfaces weren't possible, but from a distance color filters could be rotated in front of the lens and multiple images snapped with different filters. This subcontinental scale scene was imaged in green and violet on orbit 29, providing naural colors black, white, green, and violet. The other four colors are still "color blind" (red, blue, cyan and magenta). IF green is an indication of vegetation, it would seem that it's there but patchy, and that Ganymede is alive but not the verdant botanical paradise Titan is.
(I would be interested to know if there is some way to derive full color from just these two filters instead of the regular R-G-B - I'm no photo expert. There are several image pairs similar to this in green and violet, and I don't understand why they weren't done R-G-B, even though there'd have been fewer scenes covered, unless there is.)

Owing to The Urantia Book saying in paper 49 that there is an airless world with a race of non-breathing people in close proximity to our own planet, and with Ganymede appearing to have life, it is only natural to search the images carefully for any sign of human works. However, the odd time I've noticed something that looked artificial, closer inspection has revealed it to evidently be entirely natural. Below is an image showing several things I've noticed. An alternative explanation for the dark lines mentioned is that they are fractures in the crust from which molten material spewed out and created "polypy" looking surrounds on each side. (Plants or lava? -- another possible ambiguity that color imaging would surely have cleared up immediately.) However, why such linear fissures might have opened and why this sort of frond mimicking feature might be the result is puzzling, and I don't find it visually believable in all cases.

Speculations About Ganymede Life

a) Favorable Factors of Ganymede's Environment

Obviously life doesn't get a start unless environmental factors are favorable. But what is a favorable environment? What has Ganymede got that other worlds ain't got? Jupiter itself has three other moons, and Callisto is almost as large as Ganymede.

First, it orbits in a relatively quiet space zone. For example, the strength of ionizing radiation is inimical to life anywhere in the vicinity of Io's orbit. It seems unlikely any human will ever land on Io. This zone extends in considerable strength out beyond Europa, and it is likewise unlikely humans will enter that part of space.

If Europa had a very strong magnetic field, it might conceivably fend off the charged particles and keep them away from the surface. It doesn't. Ganymede is not only in a much quieter space zone, but like Earth it does have a magnetic field, which deflects the continual barrage of ionized particles from Jupiter's magnetic field as it blasts at the trailing hemisphere.

Another thing Ganymede has in spite of having almost no atmosphere, though in common with Europa and Callisto, is ozone. As on Earth, this gas should prevent dangerous UV and other radiation from the Sun from reaching the surface.

What's missing is air, and owing to that lack, open surface liquid is also absent. It is evident that Ganymedean life has to be very different from Earth life. And yet, some so-called "landslides" seen on Callisto and Ganymede, especially inside craters, have an appearance of being mud flows. On Mars there are "gully" flows down slopes in air so thin the liquid really ought to have vaporized before flowing to the bottom. Is there some volatile present within Ganymedean and Callistan soil that can flow without air? The warmest temperatures mentioned for Callisto are just below the melting point of carbon dioxide. Earth glaciers slowly flow even though they are frozen ice.

On Earth life began in the sea, but that's obviously not possible on Gnaymede. Any liquid water it has is far away from the sunlight, deep within the planet's mantle. (And volcanic vents seem unlikely on Ganymede.) Can life start in the soil on land? Plants are rooted in the soil. Certainly Earth's soil has a rich ecosystem that can be found by overturning some humous. A magnifying glass discloses a myriad of plant roots, fungi and tiny creatures. And there are ice worms that live and move inside solid glaciers on the Pacific coast from Washington to Alaska. Our experience is so limited we shouldn't presume to say life can only have a marine origin.

b) Usage of Craters by Vegetation

In image after image, we seem to be seeing vegetation growing from craters, and encircling crater rims in various ways, growing up from the peak and thus exaggerating the apparent height and steepness of the rim. What is the strange attraction of craters to plants? My guess, and it's only a guess, is that crater floors, being generally lower elevation compared to the surrounding lands, are closer to the underlying nutrients necessary to support plant growth, perhaps even to some underground liquid (or gas) table. And in fact, larger impacts may bring required nutrients to the surface. After all, the plants don't get much out of the air except sunlight, except perhaps the tenuous oxygen gas (which they more likely emit).

The upper portion of color image above, assuming the green areas are vegetation, again shows the attraction of plants to craters.

c) Life underground?: micro-meteorite protection

Many evidently vegetative features on Ganymede stick boldly up into the sky in bush and tree like configurations, even to elevations unimaginable with Earth's 9.8 m/sec^2 gravity. Others appear in a few Galileo images to be like rocks partly buried in the ground with only the top sides sticking up. It is difficult to ascertain whether this is actually the case, or whether it is simply an illusion in the rather distant, and mostly rather straight down, Galileo images.

If it is a real phenomenon, my guess is that some forms of life wish to expose as little of themselves as possible to micrometeorites, which bombard every world in our solar system but are burned up in the atmosphere on planets that have one.

Another observation is that it is likely at least some of the animal life on Ganymede is armored in some way, perhaps having shells like snails or lobsters, to ward off these otherwise lethal bullets that are bound to strike anything living out in the open from time to time. Just possibly a few imaged features are actually huge shelled creatures rather than plant life. Another possibility is that some species may live under the cover of thick vegetation.

d) Heat on Ganymede

Without a blanketing atmosphere, Ganymede gets very cold at night. While daytime temperatures may rise to at least 140K and probably well above (approximately 1/2 the temperature of Earth), at night they drop to 90K or less - colder than Titan, which is twice as far from the sun but which has an insulating atmosphere. One assumes that plants and, if there is such a thing, cold blooded animals, probably are quite dormant, even hibernating, through the 86 or so Earth hours of night. On the other hand, heat radiates away quite slowly in a vacuum, so if there are warm blooded animals, they might be able to function better than one might expect. Heat regulation in an animal body would be quite a different prospect than on an atmospheric world.

An interesting aspect to heat on Ganymede is that analysis of the nighttime temperature drops have led to the conclusion that Ganymede has a 'thin' low density layer on top of regular high density ground. This certainly describes vegetation well.

Ganymede Life Chemistry

Ganymede certainly appears to have the chemistry of life. Its spectrum is full of complex and evidently unknown organic "tholins" molecules. Tholins have been dismissed as being "thought to be abundant in the solar nebula" (prove it!) and therefore not indicative of life. However, is it reasonable to believe that such undoubtedly fragile compounds could have survived the meteoric accretion and quasi volcanic geological metamorphosis of a planet sized body? If so, why are they found only on three particular worlds and not others? Why are they either abundant or absent? And why do they evidently form only a thin "fluffy" layer right on the surface?

To me, the obvious answer is they must have appeared after the geologic upheavals of planet formation, when the surface had become stable and quiet. What chemistry formed complex substances once the geology was quiet, somewhat uniformly over the whole surface of the sphere, unless they are the signs of life that started somewhere and then spread?

In an article quoting observations of Thomas McCord (University of Hawaii, 1997, McCord said: "What we have on Callisto and Ganymede are some of the kinds of organic molecules that could be the basis for life. These are the basic ingredients."

A confusing point is, if life evolved on Ganymede, why are there other airless worlds with organic tholin compounds? Surely they couldn't have evolved life independently? Both Ganymede and Callisto seem to be covered with the complex "tholins", but they are absent on most other worlds. My surmise about Callisto is that Ganymede evolved life, and that small plant spores or Ganymedean 'algae' managed to 'hitchhike ' to Callisto on debris kicked up by meteors, found good soil, and grew there to form the dark 'fluffy' layer covering Callisto's surface. Thus, while Ganymede and Callisto are covered in organic materials, neighboring Europa, whose mostly ice surface is too radioactive to support life, has none. Ganymede is well protected by its magnetic field from Jupiter's ionic radiation which streams towards the trailing hemispheres of its satellites. On Callisto, the trailing hemisphere has less tholins than the leading. Evidently, its weak and varying magnetic field can't block all the radiation, weak though that would be so far from Jupiter, and so the trailing face is less amenable to life. Tiny Iapetus also has a covering of complex tholins, but only on the leading hemisphere. It may be that Ganymedean plant life also hitchhiked all the way to Iapetus, but as Iapetus has no magnetic field, life can't survive Saturn's radiation impinging on the trailing hemisphere. However, Iapetus orbits so far from Saturn it is often outside the irradiating magnetic field, thus non atmospheric life originating elsewhere could reach Iapetus's orbit alive.

Aside from noting its evident existence, how life works on Ganymede is a mystery to me. The oxygen in the vanishingly thin atmosphere has been thought to arise from sunlight striking the ice. It could also be a byproduct of life, and it may be used by life. On Earth and Titan, we see plants growing best near rivers, lakes or seas, or where it rains a lot, but on Ganymede there can be no liquid and no rain. Do airless worlds have some mysterious equivalent? In order to live, the plants must (I expect) be doing some equivalent of photosynthesis, obtaining energy from the Sun and converting it to some equivalent of sugars. Carbon Dioxide locked up in what might be organic tholins was noted by the Cassini on Iapetus's dark hemisphere, along with the statement that it was probably a "photochemically" produced molecule, for which one might suspect "photosynthetically". (The Cassini's upcoming and only "close" pass of Iapetus will be too distant to hope to disclose any Ganymede-like plant life.) Likewise, carbon dioxide on the ground is noted on Ganymede as well as Callisto, but there were no explanations of its origins nor remarks that it might be contained within another substance. This may be because Galileo's instruments were less refined than Cassini's newer suite rather than because of chemical differences. Sulfur is another element often associated with life disclosed by the spectral findings.

Any animal life certainly would not breathe as we know it - though the oxygen may be absorbed - or emitted - by animal life, it is far too thin for a breathing process. It would almost seem animal life would have to derive its energy more directly than the eating and breathing technique used on our atmospheric world - perhaps it might photosynthesize like the plants even though it may have brains and move about.

In the low gravity, we may perhaps see big creatures, and jumping creatures, and plants that fire out seeds or spores like bullets to spread across the land. We won't see any flying creatures, or seeds, spores or pollen drifting around, since there is no air to carry them aloft. Whatever the strange sights, there'll be no sound, though Ganymedean life might feel ground vibrations through its feet.

Inhabitants of Ganymede might view Earth somewhat as we view Uranus and Neptune - a huge sphere and obviously not a place anything could live! They obviously wouldn't communicate by sound unless they transmit and sense it through their feet, so they would probably be very difficult for us to talk to.

by Craig Carmichael,
November 23rd, 2005

Edit: Dec 11 2005 (a few more comments)
Rev: Aug 31 2006 (added Ganymede Life Chemistry section)
Rev: Feb 15th 2007 (a few minor changes and additions. Doubled size of an image in hopes more people will see the very odd things in it and wonder what they are (if not life)!
Rev: August 23 2007. Major revision. I found more images in the Galileo archive that weren't showing up when they should have in my previous searches.Added mosaic of northern Ganymede images. (AFAIK, nobody's ever bothered to put these images together before - some of them were presented upside-down on the Galileo Image Archive!) Added partial-color image from orbit 29. Added an image of Ganymede compared to Mars and Rhea, and to an Earth image of sea polyps in the harbor in Victoria BC, Earth. And added "bogus human works" image. Added "Speculations About Ganymede Life" section and edited everything, adding newer thoughts.