http://nai.arc.nasa.gov/astrobio/index.cfm NAI Ask an Astrobiologist The Kepler mission, which was launched on March 7, 2009, has completed its check-out and is now collecting data on more than 100,000 stars. Regular updates are posted at the NASA website [<a href="http://kepler.nasa.gov">kepler.nasa.gov</a>]. The preliminary data include high-precision photometry of giant planet transits and tests that indicate the Kepler system is capable of detecting transits as faint as those caused by an Earth-size world. Some of these results will be presented at the January 2010 meeting of the American Astronomical Society. However, to verify the detection of an Earth-size planet, we need to see three transits — requiring observations stretching over three orbital periods. If there are Earth-sized planets in short-period orbits very close to their stars, Kepler should make verified detections within the next year. But for Earth-size planets in the habitable zone of solar type stars, we will need a minimum of 2 years of data. We hope for such results to be available early in 2012. All of these projections depend, of course, on the number of planets and their distribution, which is precisely what Kepler is designed to tell us. There could certainly be surprises waiting for us. We hope there are. <br /><br /> <i>David Morrison<br /> NAI Senior Scientist</i> http://nai.arc.nasa.gov/astrobio/astrobio_detail.cfm?ID=8142 Europa has an ocean of liquid water larger than the oceans of Earth (with less area but much deeper), covered with a crust of ice at least several kilometers thick. The water is liquid because Europa has an interior heat source caused by stress from Jupiter tides. This is much less than the tidal heating of Io, but enough to maintain a mostly liquid ocean. There is no reason to think the ice is melting. The question of whether there could be life in the dark ocean of Europa is a fascinating one for astrobiologists. Given the presence of liquid water and an energy source from the interior, the basic requirements for life are apparently met. However, we have no idea whether life could have started in this environment. The next mission planned for Europa is a joint NASA-ESA partnership called the Europa Jupiter System Mission, which will use two robotic orbiters to conduct detailed studies of Jupiter and its moons Io, Europa, Ganymede and Callisto. The two spacecraft are planned to launch in 2020 on two separate rockets from different launch sites. The orbiters would reach the Jupiter system in 2026 and spend at least three years conducting research. This includes nearly a year with the NASA spacecraft orbiting Europa. There are no plans for a lander or rover. <br /><br /> <i>David Morrison<br /> NAI Senior Scientist</i> http://nai.arc.nasa.gov/astrobio/astrobio_detail.cfm?ID=8177 In answer to your first question, the Earth’s polarity reversal is not a periodic phenomenon. While the timing may not be random either, that assumption is consistent with the data. If it is random, and happens on average every 400,000 years, then the probability of it happening in the next thousand years is roughly one in 400. That is as good a guess as any and was the basis for my saying a reversal is very unlikely in the next few millennia. (Note that I wrote that it was very unlikely, not that “it will not occur” -- your words.) Looking at the the second question, no one knows how long a reversal takes or whether the Earth’s field ever goes to zero. What we do know is that there are no mass extinctions or other indications of any effects on the biosphere at past magnetic reversals. Thus I am not going to worry about magnetic reversals, especially when we face so many real environmental problems such as global warming, or the mass extinction we are in the midst of caused primarily by loss of habitat. If you are interested in the threat of climate change, I recommend the video of a White House forum on climate change and clean energy held October 28 [http://www.whitehouse.gov/photos-and-video/video/clean-energy-economy-forum-0]. The discussion there included some sobering comments on the worst case possibility of a truly catastrophic temperature rise in this century — heating the Earth by an amount comparable to the cooling during an ice age. The probability of this happening in this century appears to be larger than the probability of a magnetic reversal. And one distinction is that climate change is something we can influence, while magnetic polarity is not. <br /><br /> <i>David Morrison<br /> NAI Senior Scientist</i> http://nai.arc.nasa.gov/astrobio/astrobio_detail.cfm?ID=8149 SETI means the search for extraterrestrial intelligence, so by definition any such search, looking for radio signals or light pulses, is a part of SETI. There are quite a few SETI groups around the world. One of the oldest and largest is at the SETI Institute in Mountain View, California [http://www.seti.org/], and they carry out both radio and optical searches. <br /><br /> <i>David Morrison<br /> NAI Senior Scientist</i> http://nai.arc.nasa.gov/astrobio/astrobio_detail.cfm?ID=8133 I am sorry if I sometimes get irritated, but so many people who write don’t bother to read any of my previously posted answers, yet they check the box that says “I have used the search feature (blue box to the right) to verify that a question similar to mine has not already been answered.”. I would really appreciate it if anyone with a question would first see if it has been answered already. Responding to your questions: (1) There will be no change in the rotation axis of the Earth. That is not possible. (2) We don’t have any reason to expect a reversal soon of the magnetic polarity on Earth. Also, I see no reason why such a magnetic reversal on Earth would be related to the regular 22-year magnetic and activity cycle of the Sun. (3) We have never experienced a reversal of magnetic polarity (the last one took place several hundred thousand years ago). We know magnetic reversals happen at irregular intervals, but we don’t know if it happens quickly or takes thousands of years. The worst impact of a polarity change would probably be on migrating birds that use the Earth’s magnetic field for navigation. <br /><br /> <i>David Morrison<br /> NAI Senior Scientist</i> http://nai.arc.nasa.gov/astrobio/astrobio_detail.cfm?ID=8012