The Big Question

There’s a lot we know and even more we don’t know. Among the things we know we don’t know, perhaps the biggest question that exists on the minds of humans, despite the ambiguity of the term ‘life’ or even as to our own precise origin (panspermia or not), is whether or not there is life that could have developed elsewhere or separately.

When one raises the question of life, the way I see it, there are two things you distinguish. The first is complex self-replication and the other is intelligence. The benchmark for what is or isn’t intelligent is just as ambiguous, and life need not be especially intelligent to be what we might consider life.

And even the idea of self-replication is potentially confusing if you fail to distinguish an individual life form self-replicating in a pure vacuum from complex self-replicating patterns whose replication process is dependent on some environment, and energy.

Considering these distinctions, would might choose to consider stars or galaxies to be intelligent life. And we would be a loss to argue with or against such an argument using the same premises.

The Mars Science Laboratory’s Curiosity rover has recently discovered signs that Mars was once habitable for life. There were conditions such that any life that might have formed would have had access to carbon, water, and an energy source in the form of rock “chemical batteries.” However, considering both the idea that Mars and Earth are known to share meteoroid, and that extremophille are known to be able to survive the vacuum of space, it’s remotely possible that life on Mars and Earth could share a distant ancestor. However, while the energy source on Mars would have been a chemical battery, liquid water would have been dependent on solar energy.

So we look to Europa, where underneath its icy surface is thought to be a 100km deep liquid water ocean where extraterrestrial life might have learned to evolved. Evidence of a weak magnetic field by Galileo is strong evidence that there is a conducting medium beneath the surface of Europa, which could very well be a salty ocean.

Europa’s surface is thought to possibly be relatively young, between 20 to 180 million years old. The precise explanation for the formation of it’s icy surface remains a mystery. But what we do know that is the radiation levels at this surface would be enough to kill a human, and that one of the best protections against radiation is to surround yourself with water.

So out of the 4.5 billion year age of Europa, it’s thought to have only relatively recently acquired an icy surface through unknown means. But perhaps more interesting than the surface and the ocean is how the liquid water is kept liquid. Europa is the only other known location with significant amounts of liquid (heated) water (other than perhaps a large exoplanet?). In fact, Europa has more water than Earth, 2-3 times as much.

In addition to what Europa has on it’s interior and surface, there exists a toroidal cloud of mostly hydrogen and oxygen which stretches millions of miles around Jupiter. This is potentially caused by the radiation Europa experiences, kicking up water-ice molecules and breaking them down to their neutral gases which are dispersed along Europa’s orbit.

The middle blue object is Europa. The mass of the atoms dispersed along Europa’s orbit might be as much as 60,000 tons.

But the most interesting fact about Europa in relation to extraterrestrial life is not so much that it has an ocean,regardless of it having life or not, the most interesting thing is the manner in which it’s able to maintain liquid water at a significant distance from the Sun. We think that the tidal forces of gravity between Jupiter and Europa’s are enough that, over enough time, it heats up. This means that given the right type of gravitational configuration, you can generate heat and keep water in a liquid state without solar energy.

But even when you consider the energy of the Sun, the source of this energy is also gravitational potential which is converted to kinetic energy (heat) as matter is pulled together into a dense newborn star. It’s only once a star’s core is sufficiently dense that it starts to convert hydrogen to helium. The source of this density is gravitational potential, in a way not totally unlike that of Europa.

The theory about large planetary tidal waves being generate on Europa is only as old as 2008.

Strong ocean tidal flow and heating on the moons of outer planets:
http://phys.org/news148278114.html

Scientist Explains Why Jupiter’s Moon Europa Could Have Energetic Liquid Oceans:
http://www.nature.com/nature/journal/v456/n7223/abs/nature07571.html

The key parameter is to determine Europa’s “obliquity” or axial tilt (http://arxiv.org/abs/1205.3628). This is the angle between the orbiting body’s orbital axis and it’s rotational axis. Something with zero obliquity would have an equatorial plane that preciselys matches it’s orbital plane. Something with a non-zero obliquity has a tilt and would therefore have two equinox in it’s orbit.

This change in tilt while results due to obliquity will cause an atmosphere or liquid ocean will give rise to atmospheric or oceanic Rossby waves, which are a subset of inertial waves. Due to tidal forces caused by gravity, oceanic Rossby waves on Europa could be very slow east to west or west to east moving waves that can generate significant kinetic energy.

If you assume that Europa has an axial tilt of 0.1 degree, Rossby wave resonance would store 0.73x10^18 Joules (Exajoule, EJ) of kinetic energy, which is enough to heat an interior ocean and keep it liquid. This energy would be continually lost through the cooling near it’s surface, and continually replenished from the Rossby waves. The source of this energy would be gravitational potential created by Jupiter’s large gravity well. For comparison, the total energy used by commercial enterprises on Earth from 1880 to 2000, including fossil fuel and nuclear, is calculated to be roughly 17.3x10^21 Joules, or 17.3 Zettajoule (ZJ). Annual global energy consumption is about 0.5 ZJ, which equals 500 EJ annually, or 41.6 EJ monthy, or 1.3 EJ daily or .058 EJ hourly. Therefore, the kinetic energy stored by Europa’s Rossby waves might be roughly equal to about 12 hours of global energy consumption on Earth.

Beyond Europa, one might imagine an n-body system without a solar-based habitable Goldilocks zone, whereby water has been able to aggregate around a body being deformed by tidal forces generating enough heat to maintain a more or less stable interior liquid water ocean. There might even be no limit how strong these gravitational tidal forces can be.

What is interesting to note is the special significance of Jupiter as a gas giant. It’s thought that Jupiter is a natural protection system for the inner planets because of it’s high gravity. Any water-bearing comets would likely be affected by Jupiter, potentially explaining why there is so much water on Europa. Jupiter may even have a layer of water clouds.

Water on Earth, or even the Moon, may have been deposited by comets after Earth & the Moon formed, by however many comets made it past Jupiter. Therefore, while the specific configuration of Earth & it’s Moon, in it’s Goldilocks zone, and having a outer gas giant like Jupiter might be relatively rare, gas giants like Jupiter with moons are not very rare at all. It could be that there are far more moons like Europa being heated by large gas giants, which would also attract water-bearing comets.

It’s also known that ancient extremophile bacteria on Earth have been tested in high-G ultra-centrifuges and observed actually do better in terms of growth in high-G “hypergravity” environments.

The Drake equation was created by Frank Drake in 1961 based on the idea that he wanted to estimate the number of detectable extraterrestrial civilizations in the Milk Way. SETI uses this equation in it’s search for intelligent signals. The parameters in the equation are largely based off of star formation per year, number of planets per star, and the fraction of those that can support life, the fraction of those that develop to be intelligent, and the fraction of those with time to release a detectable signal into space, etc.

It occurs to me that the Drake equation totally leaves out the idea that a civilization of fish people could develop in a subsurface ocean, heated by gravity. And that since these creatures evolve in water, they wouldn’t naturally come to relate to space. They would have no atmosphere, no sky, and no real easily obtained intuition about light and radio waves. Thus, the Drake equation must be largely in error.

There should probably be a new Drake equation made that takes into account new parameters. Specifically, it should either focus on or include how many large gas giants have moons that might have significant liquid water subsurface oceans with solid ice surfaces, and what fraction of those might ever evolve to discover light & radio while never experiencing a gaseous atmosphere.

If the majority of other potential civilizations are fish people on moons with frozen water surfaces so hard they’re like granite, living in the dark, which are also in orbit around large gas giants, it might explain why we don’t see many radio signals.

Thornback ray:
http://en.wikipedia.org/wiki/Thornback_ray