And for those of you who've been asking about the videos of presentations at the Tennessee Valley Interstellar Workshop, they're now online. 2015, with New Horizons at Pluto/Charon and Dawn at Ceres, is shaping up to be an extraordinary year. Here's to the continuing effort to advance the human and robotic effort in deep space.
Speaking of spacecraft that do remarkable things, as we did yesterday in looking at the ingenious methods being used to lengthen the Messenger mission, I might also mention what is happening with Dawn. When the probe enters orbit around Ceres -- now considered a 'dwarf planet' rather than an asteroid -- in 2015, it will mark the first time the same spacecraft has ever orbited two targets in the Solar System. Dawn's Vesta visit lasted for 14 months in 2011-2012. We have the supple ion propulsion system of Dawn to thank for the dual nature of the mission. In the Dawn version of the technology, xenon gas is bombarded by an electron beam. The resulting xenon ions are accelerated through charged metal grids out of the thruster. JPL's Marc Rayman, chief engineer and mission director for the mission, explained thruster design in one of the earliest of his Dawn Journal entries: Because it is electrically charged, the xenon ion can feel the effect of an electrical field, which is simply a...
I find few things more fascinating than remote fixes to distant spacecraft. We've used them surprisingly often, an outstanding case in point being the Galileo mission to Jupiter, launched in 1989. The failure of the craft's high-gain antenna demanded that controllers maximize what they had left, using the low-gain antenna along with data compression and receiver upgrades on Earth to perform outstanding science. Galileo's four-track tape recorder, critical for storing data for later playback, also caused problems that required study and intervention from the ground. But as we saw yesterday, Galileo was hardly the first spacecraft to run into difficulties. The K2 mission, reviving Kepler by using sophisticated computer algorithms and photon pressure from the Sun, is a story in progress, with the discovery of super-Earth HIP 116454 b its first success. Or think all the way back to Mariner 10, launched in 1973 and afflicted with problems including flaking paint that caused its...
As we start thinking ahead to the TESS mission (Transiting Exoplanet Survey Satellite), currently scheduled for launch in 2017, the exoplanet focus sharpens on stars closer to home. The Kepler mission was designed to look at a whole field of stars, 156,000 of them extending over portions of the constellations Cygnus, Lyra and Draco. Most of the Kepler stars are from 600 to 3000 light years away. In fact, fewer than one percent of these stars are closer than 600 light years, while stars beyond 3000 light years are too faint for effective transit signatures. Kepler has proven enormously useful in helping us develop statistical models on how common planets are, with the ultimate goal, still quite a way off, of calculating the value of ?Earth (Eta_Earth) -- the fraction of stars orbited by planets like our own. Looking closer to home will be the mandate of TESS, which will be performing an all-sky survey rather than the ‘long stare’ Kepler has used so effectively. We should wind up with...
I'm cooking all afternoon in anticipation of a family dinner tonight. The first fruits of my labors are in the photo below. I cultivated the sourdough starter I use for this bread three years ago -- over the years, it has really developed some punch, and produces a fine, aromatic loaf. My afternoon now turns to large poultry, a country-sausage stuffing (with some of the sourdough bread as a key ingredient), various greens, beans and a chipotle-laden sweet potato dish I discovered last year. I leave it to my daughter to bring her usual spectacular salad and dessert. I want to wish all of you the best, and hope your day is going as well as mine. It's always a privilege to write for this audience.
The last time we caught up with Wendy Panero's work, the Ohio State scientist was investigating, with grad student Cayman Unterborn, a possible way to widen the habitable zone. Slow radioactive decay in elements like potassium, uranium and thorium helps to heat planets from within and is perhaps a factor in plate tectonics. In 2012, Unterborn argued that planets with higher thorium content than the Sun would generate much more heat than the Earth, allowing a habitable zone with liquid water on the surface correspondingly farther out from the star. You can read about that work and its implications in Widening the Habitable Zone. I was reminded of it because Panero reported at the recent American Geophysical Union meeting on her latest direction, a study involving the formation of the Earth's water. Recall that analysis of data from the Rosetta probe implicated asteroids rather than comets as the main delivery mechanism for Earth's oceans (see Rosetta: New Findings on Cometary Water)....
A new study of data from the Cassini Saturn orbiter has turned up useful information about, of all places, Europa. Cassini's 2001 flyby of Jupiter en route to Saturn produced the Europa data that were recently analyzed by members of the probe's ultraviolet imaging spectrograph (UVIS) team. We learn something striking: Most of the plasma around Europa is not coming from internal activity being vented through geysers, but from volcanoes on Jupiter's moon Io. Europa actually contributes 40 times less oxygen to its surrounding environment than previously thought. These findings cast one Europa mission possibility in a new light. In 2013, researchers using the Hubble Space Telescope reported signs of plume activity, which immediately called the example of Enceladus to mind. If Europa were venting materials from an internal ocean, a possible mission scenario would be to fly a probe through the plume, just as the Cassini team has done with its probe at Enceladus. The latter also has strong...
Not long after I published my thoughts on Chris Nolan's film Interstellar, Centauri Dreams regular Larry Klaes weighed in with his own take. Views on Interstellar have been all over the map, no surprise given how personal film criticism can be (take a look at the critical reception of Bladerunner over the years). I like the point/counterpoint aspect of what Larry does here, and while I imagine most readers have seen the movie by now, his criticisms may provoke a few more viewings and, I hope, a look at Kip Thorne's excellent book on science in the making of the film. By Larry Klaes When I first heard about the existence of the film Interstellar, I was initially hopeful yet cautious. Most science fiction, especially these days, is some variation on Star Wars, which is often about as scientific and science fictional as the Harry Potter series. Yet Christopher Nolan and his team insisted they were striving hard to stick to REAL science with their production: They even had the famous...
Looking forward from winter into spring in North America -- unfortunately still a few months out -- I can thank Earth's obliquity for a seasonal change I enjoy more every year. Obliquity is the angle that our planet's rotational axis makes as it intersects the orbital plane, which in the case of Earth is 23.5°, so that when we reach the summer solstice, the north pole of the planet tilts toward the Sun by this angle. At winter solstice, the pole is tilted away by the same amount. Our Solar System's most extreme case of obliquity is Uranus, where the angle is a whopping 97.8°. Imagine a planet where the north pole points all but directly at the Sun, cycling through a year where the southern pole will eventually do the same. I'm reminded of Stephen Baxter's novel Ark (Roc, 2011). Here, interstellar travelers come to a planet they hopefully designate Earth II (82 Eridani is its primary). Alas, the obliquity turns out to be 90 degrees, kicking off extreme seasonality. In this...
What exactly is the shock wave that Voyager 1 encountered earlier this year, a wave that is still propagating outward, according to new data from the craft? Researchers at the Jet Propulsion Laboratory refer to it as a 'tsunami wave,' a simile that reminds us of the devastating effects of roiled water as it encounters land following an earthquake or an impact in the ocean. But in this case the cause is a coronal mass ejection (CME), in which the Sun heaves out a magnetic cloud of plasma from its surface, generating a pressure wave. As this JPL news release explains, the outgoing wave runs into charged particles in deep space -- interstellar plasma -- creating the disturbance. In all, Voyager 1 has experienced three of these shock waves, with the most recent first being observed in February of 2014 and still continuing. The new data were presented on December 15 at the American Geophysical Union meeting in San Francisco by Don Gurnett (University of Iowa), who is quoted as saying...
A new paper out of George Mason University tackles the subject of planets deformed by tidal effects in close proximity to their star. It's a useful study for reasons I'll explain in a moment, but first a digression: I once had the chance to talk physics with the late Sheridan Simon, who besides being a popular lecturer on astrophysics at Guilford College (Greensboro, NC) also had a cottage industry designing planets for science fiction writers. Simon loved oddly shaped planets and because the Super Bowl was coming up, he had taken it upon himself to design a planet in the shape of a football, just to see what would happen if a place like this actually existed. "And you know what? It works," the bearded, exuberant Simon said with a grin. "But when you model what it looks like from space, the atmosphere is a problem. It looks plaid!" Simon played around with planets of every description, and if you'd like to see him at work on a planetary system around Tau Ceti, check what he developed...
The impact at Tunguska, Siberia on June 30,1908, evidently a small asteroid, devastated 1300 square kilometers, which works out to be the equivalent of a large metropolitan area. June 30, 2015 is thus an appropriate date to launch Asteroid Day, a global awareness campaign to put the issue of dangerous impacts in front of as many people as possible. An early December press conference at the London Science Museum, hosted by Lord Martin Rees, UK Royal Astronomer, announced the campaign and released a declaration of needed action: Employ the available technology to detect and track near-Earth asteroids that threaten human populations A rapid hundred-fold (100x) acceleration of the discovery and tracking of NEOs Global adoption of Asteroid Day on June 30, 2015, to heighten awareness of the asteroid hazard and our efforts to prevent future impacts The list of scientists, business leaders and artists behind the 100x Declaration, as it's being called, is an impressive one that includes Jill...
Lunar Mission One is an interesting private attempt to put a payload on the lunar surface, a crowdsourced project aimed at doing good science and deepening public participation in spaceflight. Remembering the Apollo days, I'm always interested in seeing what can be done to renew interest in space, and having the chance to make a contribution toward such a self-starting space mission is undeniably attractive. As witness Lunar Mission One's pitch on Kickstarter, which has aimed for an ambitious £600,000 and has already raised £520,341. That figure is as of this morning, with five days to go in the attempt, and it's clear enough that £600,000 won't buy a lunar mission of considerable complexity, as this one is. But it's enough to take an effort that has been seven years in the building to the next level, which means establishment of working management teams and the beginning of procurement planning and risk assessment. That turns what has been a part-time volunteer project into a...
Where did the water in Earth's oceans come from? It's an open question, but new data from the Rosetta mission, in particular its ROSINA instrument (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) indicate that terrestrial water probably did not come from comets like 67P/Churyumov-Gerasimenko, around which Rosetta has been orbiting since August. There is little doubt that water reached Earth through bombardment from small bodies early in the planet's history, but the Rosetta findings sharpen the question of where these objects came from. Image: This composite is a mosaic comprising four individual NAVCAM images taken from 19 miles (31 kilometers) from the center of comet 67P/Churyumov-Gerasimenko on Nov. 20, 2014. The image resolution is 10 feet (3 meters) per pixel. Credit: ESA. At work here is analysis of the ratio between hydrogen and deuterium, a heavy form of hydrogen with one proton and one neutron in the nucleus (common hydrogen lacks the neutron). This D/H ratio on...
My friend Frank Taylor was in town over the Thanksgiving holiday, having flown in from South Africa. With his wife Karen, Frank has spent the years since 2009 circumnavigating the globe aboard a 50-foot catamaran called Tahina, an adventure chronicled with spectacular photography on the Tahina Expedition blog. I highly recommend the site for anyone interested in travel and the sea, not to mention how high tech has transformed the ancient art of sailing. But when we spoke recently just before Frank returned to Africa, he had another kind of high tech in mind. Specifically, what had I thought about the film Interstellar? I haven't delayed my comments on the movie intentionally, but I was slow in getting to see it, missing the opportunity at the end of the Tennessee Valley Interstellar Workshop and then getting involved in recent activities including the One Earth New Horizons Message workshop at Stanford. I also wanted to read Kip Thorne's The Science of Interstellar (Norton, 2014) and...
No spacecraft has ever traveled further to reach its primary target than New Horizons, now inbound to Pluto/Charon. From 4.6 billion kilometers from Earth (four hours, 26 minutes light travel time), the spacecraft has sent confirmation that its much anticipated wake-up call from ground controllers was a success. Since December 6, New Horizons has been in active mode, a state whose significance principal investigator Alan Stern explains: "This is a watershed event that signals the end of New Horizons crossing of a vast ocean of space to the very frontier of our solar system, and the beginning of the mission's primary objective: the exploration of Pluto and its many moons in 2015." Image: Pluto and Charon, in imagery taken by New Horizons in July of 2014. Covering almost one full rotation of Charon around Pluto, the 12 images that make up the movie were taken with the spacecraft's best telescopic camera - the Long Range Reconnaissance Imager (LORRI) - at distances ranging from about...
We're going to be bringing both space- and ground-based assets to bear on the detection of rocky planets within the habitable zone in coming years. Cool M-class stars (red dwarfs) stand out in this regard because their habitable zones (in this case defined as where water can exist in liquid form on the surface) are relatively close to the parent star, making for increased likelihood of transits as well as a larger number of them in a given time period. Ground observatories like the Giant Magellan Telescope and the European Extremely Large Telescope should be able to perform spectroscopic studies of M-class planets as well. So consider this: We have a high probability for planets around these stars (see Ravi Kopparapu's How Common Are Potential Habitable Worlds in Our Galaxy?), and then factor in what Ramses Ramirez and Lisa Kaltenegger have, the fact that before they reach the main sequence, M-class stars go through a period of 'infancy' that can last up to 2.5 billion years. It's an...
What trajectory will our civilization follow as we move beyond our first tentative steps into space? Nick Nielsen returns to Centauri Dreams with thoughts on multi-generational projects and their roots in the fundamental worldview of their time. As the inspiring monuments of the European Middle Ages attest, a civilizational imperative can express itself through the grandest of symbols. Perhaps our culture is building toward travel to the stars as the greatest expression of its own values and capabilities. Is the starship the ultimate monument of a technological civilization? In addition to continuing work in his blogs Grand Strategy: The View from Oregon and Grand Strategy Annex, Nielsen heads Project Astrolabe for Icarus Interstellar, described within the essay. by J. N. Nielsen If interstellar flight proves to be possible, it will be possible only in the context of what Heath Rezabek has called an Interstellar Earth: civilization developed on Earth to the degree that it is capable...
Yesterday's post about planets in red dwarf systems examined the idea that the slow formation rate of these small stars would have a huge impact on planets that are today in their habitable zone. We can come up with mechanisms that might keep a tidally locked planet habitable, but what do we do about the severe effects of water loss and runaway greenhouse events? Keeping such factors in mind plays into how we choose targets -- very carefully -- for future space telescope missions that will look for exoplanets and study their atmospheres. But the question of atmospheres on early worlds extends far beyond what happens on M-dwarf planets. At MIT, Hilke Schlichting has been working on what happened to our own Earth's atmosphere, which was evidently obliterated at least twice since the planet's formation four billion years ago. In an attempt to find out how such events could occur, Schlichting and colleagues at Caltech and Hebrew University have been modeling the effects of impactors that...
A common trope from Hollywood's earlier decades was the team of explorers, or perhaps soldiers, lost in the desert and running out of water. On the horizon appears an oasis surrounded by verdant green, but it turns out to be a mirage. At the University of Washington, graduate student Rodrigo Luger and co-author Rory Barnes have deployed the word 'mirage' to describe planets that, from afar, look promisingly like a home for our kind of life. But the reality is that while oxygen may be present in their atmospheres, they're actually dry worlds that have undergone a runaway greenhouse state. This is a startling addition to our thinking about planets around red dwarf stars, where the concerns have largely revolved around tidal lock -- one side of the planet always facing the star -- and flare activity. Now we have to worry about another issue, for Luger and Barnes argue in a paper soon to be published in Astrobiology that planets that form in the habitable zone of such stars, close in to...
