There was a good turnout of members at the December meeting of Keighley Astronomical Society. The guest speaker was Mr Richard Turner from neighboring Harrogate Astronomical Society.
Mr Turner started off with the prospect of microorganisms existing on Mars and probes of increasing complexity that will be going there in the years to come. The core of his presentation was the life search in the outer Solar System. Having an environment with liquid water makes the possibility of life forms more plausible. For this reason, astrobiologists consider the space extending from the orbit of Venus to the orbit of Mars around the Sun as a “Goldilocks zone”. Venus is super-hot at the surface because of an extreme greenhouse effect from high levels of carbon dioxide in its atmosphere, but it’s actually far enough from the Sun that it would be cool enough for liquid water if its atmosphere were different. Mars is cold, but warm enough for liquid water; in fact, scientists are almost certain that water flows on the Martian surface from time to time.
Mr Turner took us out to the orbits of Jupiter and Saturn, the outer Solar System, sunlight is too weak for liquid water to flow on the surface of a planet or moon, so it’s beyond the traditional limit of a Goldilocks zone, but liquid water can exist below the surface when there is a source of heat other than the Sun. Over the last 20 years, planetary scientists have accumulated evidence of large amounts of liquid water existing under the icy surfaces of worlds in the outer Solar System. The two that have received the most attention are Jupiter’s moon Europa and Saturn’s moon Enceladus, because measurements from space probes show that each has an entire ocean.
The ocean is covered with ice, which keeps the liquid water beneath from evaporating into space, but while flying by Enceladus, NASA’s ‘Cassini’ probe had photographed plumes of water gushing from geysers in the Enceladus ice. Mr Turner explained, that the ocean of Enceladus may be accessible to a probe that could be sent in the near future. As opposed to being blocked by the ice the covers it, the ocean may be reached through a geyser, and the fact that there are geysers in the first place suggests that the portions of the ice layer might not be so thick that a robot from Earth couldn’t drill through it and reach the ocean.
So what keeps these moons warm enough to maintain global oceans of water below their freezing surfaces? Well Mr Turner pointed out tidal heating. Europa travels around Jupiter in an elongated orbit, causing Jupiter’s immense gravity to tug on the moon with varying amounts of strength as Europa moves. Thus, Europa is constantly squeezed and stretched and this generates heat deep inside the moon. The same thing happens to Enceladus as it orbits around Saturn.
As for missions to these moons, Mr Turner highlighted that NASA is currently preparing a Europa mission to launch in the early 2020s. Instruments are being selected to study Europa from orbit to acquire details about its environment relevant to the search for life forms, such as whether the subsurface ocean releases plumes of water through the ice as Enceladus does.
The Europa mission may include a small landing craft to conduct experiments on the ice surface, and possibly on protruding liquid water if any plumes are located. It’s not clear yet what type of experiments would go on such a lander for the Europa mission, but NASA has begun flirting with an idea of mission to Enceladus specifically to seek life forms. It would be called the Enceladus Life Finder (ELF) and it would be a follow up to the Cassini probe orbiting Saturn now that will continue to perform Enceladus flybys. Launch of the ELF would probably take place well into the 2020s, or beyond, but the experiments to search for life could be fairly sophisticated. ELF tests could be looking for evidence that water samples on Enceladus act preferentially on certain molecules versus others, for instance on fatty acids with on odd number of carbon atom versus those with an even number of carbon atoms. Experiments looking for differences in chemical interactions between water samples and molecules that are chemically “left handed” verses those that are chemically “right handed” also could be in the works. This level of sophistication would be important to avoid scenarios similar to what happened in NASA’s Viking mission, when one test seemed to have.detected life, but other tests seemed to detect chemical activity in Martian dust that was not the result of life.
As this was the last monthly meeting of the year, and just prior to Christmas; the members were treated to festive fair and goodies, with the request that a donation be made to the society Christmas charity. This year the chosen charity was the Madame Curie Hospice in Bradford. The sum raised on the night was £87.22p. That’s the largest sum the society annual charity collection has raised. So well done to all of you.
Society chairman Paul Neaves welcomes December guest speaker Mr Richard Turner to Keighley Astronomical Society
The December meeting commences
The surface of Jupiter’s icy moon Europa
Mr Turner taking questions at the end of his presentation
Plums of water photographed coming from the southern pole of Saturn’s moon Enceladus
A discussion on the prospects for life in our Solar System