The Solar System Laboratory

Scientists like to test materials, events, things under different conditions: changing the variables to see how the subject responds. This works well for items that can be tested in a laboratory, but what about those that are just too small? Or even too big?

The small has been covered: particle accelerators like the ones at CERN have managed to conduct particle collisions, some of the smallest interactions in our universe. Computer models have also shown to prove their use.

So what about the big? Computer models are useful again, but they never give you the real answers. The clue is in the title, they are models.What happens in reality could be completely different.

Earth, credit NASA

Earth, credit NASA

Weather systems are one of those things that are just impossible to bring into a lab. Can you image? A tornado in the lab turning the desks upside down, blowing apparatus all over the place and generally causing chaos, damaging anything it touches. This would be detrimental to the work being done. So, meteorologists use computer models to see how weather systems behave.

It’s a little tricky however, to see what would happen to our weather systems if we removed or changed some of the different variables that influence it. What if we dropped the temperatures, what would happen? With all the talk of global warming, a lot of models are being run to see how the Earth would be affected by rising temperatures. But what if we removed mountains? How would that affect our weather systems? Or what about removing the crust entirely, what would happen then? We would just be a small core surrounded by hundreds of kilometers of atmosphere.

These are questions to which the solutions may not be directly useful for society, but they are interesting none the less. One way to study these conditions would be to look beyond our own planet, and out into our solar system. Although small in the grand scheme of things, it is home to a fantastic variety of environments. This is something that Dr Leigh Fletcher, from Oxford University studies.

Giant planets are reservoirs for initial material that forms in the solar system. For solar system to form, small rocky bits floating around aggregate to form protoplanets. The inner solar system contained a lot of heavy metals: refractory materials which went on to create the terrestrial worlds. The outer solar system had the ices – materials that formed in very low temperatures: water, CO2, methane, and ammonia gases.

When the protoplanets reached certain size, they became so heavy that they started to “suck in” any nebula gases surrounding them. Nebula gas is now seen as the atmospheres of the giant planets, and deep in their interiors there are still these protoplanets; rocky cores left over from birth of solar system.

“I like to think of the giants as windows onto our past. If we can understand the composition of these giant worlds, then we might have a way of probing what the solar nebula looked like 4.5 billions yrs ago when these planets started to condense and agglomerate out of that initial soup of material.” Dr Leigh Fletcher, SPA meeting, October 2012.

So what can these nearest neighbours of ours teach us about our own planet? The larger planets in the outer solar systems have very similar features to each other. Both the gas and ice giants have a banded structure, which can been seen through telescopes. These bands are gases that have been collected into clouds of different gases. Gas giants like Jupiter appear to have large numbers of belts and zones on their surfaces, which are blown by jets moving rapidly from east to west. Ice giants, like Uranus, also contain these bands in their atmospheres.

A lot of parallels to be drawn from banded activities on gas and ice giants. We have started seeing this type of banding on Earth’s oceans. Belts and zones seem to be ubiquitous features that appear throughout the solar system.

Each of these giant planets also undergoes seasonal changes as they spin on their axes and move around the sun. By looking at giant planet atmospheres we can learn about our own atmosphere on Earth, but in different contexts that cannot be simulated. Each planet in solar system acts as an individual experiment, testing the Earth’s atmosphere under different conditions.

Jupiter, credit NASA/JPL/USGS

Jupiter, credit NASA/JPL/USGS

Jupiter is like control experiment: what would a planet be like without the effect of seasonal change: it only has a very tiny axis tilt 3 degrees.Saturn and Neptune have tilts that are closer to that of Earth, between 23-26 degrees, so they experience similar seasons to us, but over much longer time scales. Saturn has a timescale of 7.5 years, and Neptune has one of 40 years. Uranus is the odd-ball. the theory goes that after Uranus was formed, a gigantic impact served to knock the planet onto its side, which now orbits edge on. This means the bands run from north to south, rather than east to west.

Each planetary tilt will affect the seasonal changes differently. Studying the atmospheres of the rest of the planets in our solar system can provide context; it is an ensemble of cases that allow us to study our own atmosphere better.

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