Bakersfield Night Sky – December 3, 2016
By Nick Strobel
The semester is almost through at Bakersfield College. Finals are this coming week and this Thursday, December 8, is the last show at the William M Thomas Planetarium for the fall season. The William M Thomas Planetarium will present the popular holiday show “Season of Light” on December 8 from 7:30 to 8:45 p.m. Tickets for the show are still available at the BC Ticket Office and online through Vallitix.
This holiday season is also the time when most telescopes are purchased. Be sure to check out Sky and Telescope’s buying guide “How to Choose Your First Telescope” at www.skyandtelescope.com/astronomy-news/types-of-telescopes/ before spending the hundreds of dollars on that telescope for yourself or for someone you love. On that website you’ll also find reviews of the various types of telescopes, eyepieces, and other accessories.
On Monday, NASA will release the latest issue of its “Spinoff” publication that highlights NASA technologies that are benefiting life on Earth in the form of commercial products (see http://spinoff.nasa.gov). I was reminded of this when reading a story over Thanksgiving break about the use of “lidar” (light detection and ranging) technology to help archaeologists find fossils and bones hidden below the surface. The lidar instrument can be used to produce a “bare-earth” version of the surface that strips away all of the vegetation and making ancient structures more obvious.
Lidar has been around since the Apollo program and it will be used on the OSIRIS-REx mission to map the asteroid Bennu when it begins orbiting the asteroid in 2018. While lidar has been used on previous spacecraft, the one on OSIRIS-REx will be the first scanning one on a planetary mission. That means the instrument will be able to move independently of the spacecraft’s motion providing much greater spatial coverage and resolution than previous missions.
Other Thanksgiving break reading included reading about the so-called “martian cauliflower” formations found by the Mars Exploration Rover “Spirit” in the Columbia Hills of Gusev Crater back in 2007. The cauliflower is not stuff left behind by picky martian children who did not want to eat their vegetables but, rather, outcrops of opaline silica in ancient volcanic hydrothermal vents. At the time, the finding was interesting but not that significant. Two researchers, Steven Ruff and Jack Farmer took another look at the microscopic images and spectra of the martian outcrop after they had studied an active hot spring at El Tatio in northern Chile. El Tatio is at a very high elevation in a very dry part of Chile that gets more UV exposure than hot springs closer to sea level. It’s probably the most Mars-like hot spring location we’re going to find on Earth.
What was so interesting about this paper published just a few weeks ago in “Nature Communications” is that the structures and spectra at El Tatio provide the best match to what Spirit found in Gusev Crater and those structures are produced by a combination of biotic and abiotic processes. “Biotic” means “biological” of life. That means those features are potential biosignatures. A “biosignature” is something that is a positive indicator of life and that could not be made by non-biological processes. While the martian cauliflower formations do NOT mean that we have discovered life on Mars, the formations do mean that those features in Gusev Crater are worth sending the 2020 Mars Rover to look at in more detail and prepare samples to return to Earth by a later mission.
Reading about potential biosignatures led me to view a great webinar about exoplanet biosignatures. (What wonderful stuff I can explore when I have a break from the teaching and committee work of a faculty member!) The webinar was given by a couple of recently-minted PhD’s (Giada Arney and Eddie Schwieterman) from my alma mater, the University of Washington. They focused on the use of molecular oxygen, ozone, and methane as biosignatures because those molecules can be detected in exoplanet atmospheres through spectroscopy from many light years away.
A lot of research is being done on figuring out what biosignatures could be seen on exoplanets and how the amount of those biosignatures would change through a planet’s history. For example, for about half of Earth’s history, there was not enough oxygen in our atmosphere to be detectable by any E.T. in another star system. Also, complex, multi-cellular life came onto the scene “only” 800 million years ago. Compared to the 4600 million-year age of Earth, that’s fairly recent. What if we’re looking at an exoplanet during the big chunk of its existence when life hasn’t been around long enough to produce a detectable change in its atmosphere?
The research into exoplanet biosignatures is also looking into how to avoid the “false positives”—test results that incorrectly indicate life is present. It turns out that a particular radiation environment of certain types of stars could produce a lot of oxygen in an exoplanet’s atmosphere under a certain set of conditions. See https://youtu.be/yxtRr9hL99M for more about that and how it applies to the closest exoplanet to us, Proxima Centauri b.
The evening sky charts below show the positions of the planets at 6:30 p.m. and the bright winter constellations rising at 10 p.m.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com