Jovian Life: The Moons Versus the Planets: Part Two

In our solar system, the planets are divided between the inner terrestrial planets (Mercury, Venus, Mars and of course the Earth) and the outer gas giants, collectively called the Jovian planets (after Jupiter, but including Saturn, Uranus and Neptune), which along with their many moons form the Jovian system. Since it’s easier to look in our own planetary backyard neighbourhood first for alien life, there’s been much speculation about what pieces of solar system real estate, if any, might be suitable abodes for extraterrestrial life. While Mars has always been top-of-the-pops, a once heavily favoured Venus fell by the wayside a while back, only to be replaced with a few bits of real estate somewhat further out. It’s those “somewhat further out” bits of real estate that are now under-the-gun. While most speculation is on selected Jovian satellites, I put the accent on the parent bodies.

Continued from yesterday’s blog…

Now on to the major players! It’s time to introduce the main players, Jupiter, Saturn, Uranus and Neptune, and those four essentials: CHON, environment, mixing and energy. If there is life-as-we-know-it on these four planets, then we need CHON, we need a proper environment, we need mixing to bring essentials together at one time and place, and we need a source(s) of energy.

One clarification is in order first. Although the Jovian planets are usually called “gas giants”, that is a slight misnaming. While it’s true that relative to Mercury, Venus, Earth and Mars, the Jovian planets are indeed great big balls of gas, they still must have at their centre a solid rocky core, due to, if for no other reason, that over 4.5 billion years of their existence, asteroids, maybe even small planets, meteors, dust, and comets have all slammed into them. The rocky stuff, ultimately, must sink to the bottom forming a solid heavy element core. With that clarification made, let’s see what there is to be speculated upon. 

Jupiter: CHON: Jupiter, a gas giant, is composed mainly of molecular hydrogen (the H in CHON) and helium (much like the Sun’s composition and in roughly the same ratios). There are certainly ammonia (probably as ice crystals) and ammonia compounds (like ammonium hydrosulphide) in the atmosphere, adding nitrogen (the N in CHON) to the mix. Methane (which contains the C in CHON), as does the carbon contained in carbon dioxide and carbon monoxide are also present in the upper atmosphere. Water vapour (the O in CHON) is certainly present, even though in small proportions relative to hydrogen and helium. The colourful bands of latitude could easily be suggestive of complex, even organic chemistry involving not only CHON but sulphur and phosphorus and other trace elements. The upper atmosphere of Jupiter contains small amounts of simple hydrocarbons such as ethane and acetylene, which forms from methane under the influence of the Sun’s ultraviolet radiation and the highly charged particles incoming from the Jupiter’s magnetosphere.   

Jupiter: Environment: There’s no disputing that the cloud tops are bitterly cold; the deep interior is way too hot. But, that alone suggests that there will be a Goldilocks area in-between, probably extending vertically for hundreds of kilometres, and extending as well horizontally around the globe. That volume, given Jupiter’s size, comprises a lot of Goldilocks territory. 

Jupiter: Mixing: Since Jupiter has a very hot interior core and the top of the atmosphere is extremely cold, and since heat rises and cold descends, that alone suggests that mixing in Jupiter’s primarily gaseous/quasi-fluid body must take place. Quite apart from that, all one needs to do is view time-lapse photography of Jupiter’s upper atmosphere to see all the turbulent motion that takes place. A tranquil pond Jupiter isn’t.

Jupiter: Energy – Solar energy is highly unlikely to drive any Jovian biology because the atmosphere is very thick, and just like with our terrestrial oceans, things get very dark very quickly as one descends. However, chemical energy is a possibility, like that which drives terrestrial hydrothermal vent communities. Then there’s infrared (instead of visible) radiation. Jupiter radiates much more heat that it receives from the Sun, the heat being slowly radiated outward from Jupiter’s original quota of primordial heat energy largely stored in the core of the planet.  Jupiter is a fantastic place to visit if you’re fond of thunderstorms. Lightning really lights up the Jupiter’s skies. Lightning is a prime source of energy for driving chemical reactions. Translated, all up, Jupiter is awash with potentially useful energy sources to drive any local biology.

Saturn: CHON: The atmosphere of Saturn (which is what the mainly planet is – a ball of gas) consists of one hell of a lot of molecular hydrogen and some helium, a really skewed ratio relative to those elements found in the Sun, but that’s another story. However, it does explain why Saturn, if you could find a freshwater ‘pond’ large enough, would float in it! That aside, the atmosphere contains trace amounts of ammonia (there’s your nitrogen), acetylene, ethane and methane (and your carbon), plus phosphine - all have been detected. The upper atmosphere has clouds composed of ammonia crystals, while the lower atmospheric clouds appear to be composed of ammonium hydrosulfide and/or water (thus some oxygen).

Saturn: Environment: The same discussion that applies to Jupiter applies to Saturn, although because Saturn is a smaller planet (albeit massive relative to Earth) the habitable volume of Saturn’s quasi-liquid atmosphere will be somewhat less.

Saturn: Mixing: Saturn also has that hot interior, cold exterior dichotomy that exists in this gaseous/fluid planetary ball. It’s akin to the convection that occurs when you heat water on your stove. Hot water rises; cooler water descends. And while not as dramatic as time-lapse films of Jupiter’s atmosphere, it’s also obvious that Saturn’s visual ‘surface’ is anything but tranquil. In fact the winds on Saturn are among the highest of any planetary body in the solar system. However, being farther from the Sun, Saturn’s chemistry is not going to be quite as dramatic as closer-in Jupiter, and thus Saturn’s atmospheric ‘surface’ is a lot blander appearing.

Saturn: Energy – As is the case for Jupiter, and for much the same reason, solar energy (photosynthesis) is out on Saturn; chemical energy and infrared radiation (heat energy) will be the way to go. Saturn also radiates more heat that it receives from the Sun – two and a half times more in fact; Saturn is also a fantastic place to visit if you’re fond of thunderstorms. Lightning also lights up the skies of Saturn.

To be continued...