What is our best bet for finding life outside of Earth? We could detect biosignatures on exoplanets, but at best we would be inferring the probably existence of some kind of life, but not be able to examine it directly. Therefore the most intriguing questions about extraterrestrial life will go unanswered. If we detect life in our own solar system there is the possibility of getting samples of that life in the not-to-distant future. Mars, as hostile as it is, is the closest thing to Earth in the solar system so we have focused a lot of attention there.

In the last few decades, however, another possibility has gained attention – life evolving in the subsurface oceans of icy worlds, most notably the moons Europa of Jupiter and Enceladus of Saturn.  In 2024 NASA will be sending the Europa Clipper mission to Jupiter. The craft will enter into an orbit around Jupiter designed to give it multiple close approaches to Europa. It is outfitted with a host of instruments to study the icy moon – a mass spectrometer to examine the constituents of the surface ice, a magnetometer, radar to probe the structures under the surface, and many others. The probe will arrive at Jupiter around 2030 so until then scientists are busy trying to learn as much about Europa as possible to make the best of the Clipper mission.

While the mission is not designed to directly detect life on Europa, it is designed to answer very specific questions about the plausibility of life. Being a frozen world distant from the sun (the sun’s light intensity is only 4% that of Earth’s), how could life evolve and survive? Beneath the icy shell of Europa is briny water, water mixed with minerals that is partially frozen but also liquid enough to have convection. Below the brine is a large liquid ocean, with more than twice the volume of water as in the oceans of Earth. Europa is not frozen solid (which it would be, given its size and distance from the sun) because of tidal forces from its massive parent, Jupiter. These tidal forces reshape Europa causing friction that heats the planet. Beneath the subsurface oceans scientists predict there are volcanoes on the sea floor.

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The percentage of world electricity generated by wind and solar energy hit 10% in 2021 according to a recent analysis. Total clean energy (including nuclear, hydro, geothermal, and bioenergy) was 38% of world electricity, exceeding coal at 35%.  Gas was 22%, for a total fossil fuel contribution of 57%. Also, total demand for electricity rose sharply in 2021, partly due to the bounce back from the pandemic, with coal rising 9% total and making up most of the increased demand – so this is a very mixed story.

According to the analysis there are two major forces at work across the world in determining the relative growth of the various sources of electricity, economics and regulations. In political fights over energy (including frequently in the comments to this blog) people will often assume one or the other factor is the only or the major factor involved. For example, the argument has been explicitly made that economics is the only relevant factor and policy is therefore irrelevant, but that is demonstrably not true. Neither is the notion that we can totally control the energy sector through policy without consideration of economic factors. That approach is likely to lead to policy overreach with backlash and unintended consequences. Both factors are involved, and a rational energy policy should consider the relevant economics.

For example, coal surged in 2021 because it is cheap relative to its major competitor, gas. Both rose in price, but gas rose much more than coal, so coal predominated. However, wind and solar are cheaper than both, so they also rose significantly. Even though they are now the cheapest option for adding new capacity, they were outpaced by coal because of regulations and infrastructure – showing that price alone is not the only determining factor.

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