by Paul Gilster | Feb 23, 2009 | Culture and Society |
Prioritizing the Outer System
Europa or Titan? Jupiter or Saturn? NASA and the European Space Agency, faced with the dilemma of choosing between competing missions, apparently settled on both, with the Europa Jupiter System Mission likely to be implemented first. Here we’re talking about two robotic orbiters, launched on separate spacecraft in 2020, with arrival in Jupiter space in 2026. The two orbiters will orbit Europa and Ganymede respectively, while the later Titan Saturn System Mission would include a NASA orbiter and an ESA lander and research balloon. Both missions thus move forward for further study.
I note all this in the context of what will surely be ever increasing interest in Europa following the publication of Richard Greenberg’s Unmasking Europa: The Search for Life on Jupiter’s Ocean Moon. I’ll be talking to Greenberg tomorrow and reporting on our conversation soon, but I do want to quote him on a particular point right away, relevant as it is to mission planning:
“…when a spacecraft returns tens of thousands of or hundreds of thousands of images, most of that data is stored away and never studied in detail — or studied at all. Occasionally a graduate student or other persistent scholar might revisit old data as part of a research project, but there is relatively little funding or motivation for digging through archived material. And the older the data get, the more difficult it is to retrieve and understand. Instead, the big money and attention are lavished on the fresh new images from the latest mission.
Why is this a problem? Because we design new missions based on our understanding of the targets we plan to study. And if we misinterpret our results — Greenberg convincingly argues that this has happened with our analyses of the thickness of Europa’s ice — then we might design missions down the road that don’t take advantage of the real situation on the surface. We need new missions, of course, but we shouldn’t forget the vast backlog of data that can provide many of the answers we need about Europa through patient analysis long before the Europa Jupiter System Mission ever lifts off.
And looking beyond this next Jupiter mission, we need to find out for sure how thick the surface is before we design an even later mission around the idea of drilling through tens of kilometers of ice. Greenberg again, from Unmasking Europa:
If we confirm that we might put a lander at just the right place next to an active crack so that within a few hours fresh sea water will slosh to the surface, or that frozen sea life are spread over the surface by the variety of ways that oceanic water reaches the surface, then we would design very different mission strategies than if we believe that everything interesting is sealed off more than 20 km down.
We’re in a new era of science, one in which data accumulate so quickly that we often don’t have the funding or the time to do the kind of detailed analysis necessary. This is a challenge for any scientist, but especially those planning missions to targets as provocative as these. Add to this the potential for data loss as we continually upgrade and change data formats and hardware and you can understand why managing digital resources is going to be a key aspect of future planetary exploration.
Changes to Centauri Dreams
Now and then when you log on to Centauri Dreams in the next few weeks, don’t be surprised to find yourself looking at unexpected formatting. I’m working on various software changes behind the scenes that will give me more flexibility in posting and managing the information flow. And because I am anything but a skilled coder, you can expect the occasional mistake as I tweak the options. Things will eventually return to normal under a slightly revised format, but bear with me as I leap into the unknown.
Several of you have noticed the favicon the site has added. A ‘favicon’ is the little image you can see in your browser’s address bar when Centauri Dreams is loaded, immediately to the left of the Web address. Many sites these days have them, but reader Piotr Mazik noticed I didn’t. Actually, I had tried to implement one, but ham-handedly had created the image in the wrong format. So Piotr was kind enough to make one himself and pass it along. In such ways, large and small, I benefit from the readership here every day, and send thanks to Piotr and all who have made suggestions and come up with helpful tips related to keeping Centauri Dreams online.
Space, Propulsion and Energy Forum in Huntsville
The Space, Propulsion and Energy Sciences International Forum (SPESIF 2009) kicks off tomorrow in Huntsville at the Von Braun Center and runs through the 26th. Although I can’t be there, I’ll be interested in reading a transcript of Les Johnson’s report on interstellar propulsion research, which leads off the meeting. Johnson (NASA MSFC) has been looking at interstellar options for a long time, having once served as the head of the provocatively titled Interstellar Propulsion Project, which NASA later folded into the In-Space Propulsion Program at the Alabama facility.
Now deputy manager for the Advanced Concepts Office at MSFC (and author, with Greg Matloff and Giovanni Vulpetti, of the excellent Solar Sails), Johnson will also be addressing solar sail options. Have a look at the site, where numerous abstracts and preprints are made available. Among other presentations, I was attracted by Gerald Jackson’s session on antimatter. Jackson (Hbar Technologies, Chicago) has been working on antimatter harvesting in space and, along with Steve Howe, has been a proponent of the hybrid antimatter/fission sail concept we’ve discussed earlier here on Centauri Dreams. His study for NIAC on space-based antimatter retrieval is still available at the NIAC site, despite that organization’s demise, and a preprint of his SPESIF talk is also online.
As a former medievalist with an interest in Icelandic studies, I’m particularly looking forward to reading “Space Exploration and the Greenland Norse; A comparative Study on the Application of Technology for Exploration,” by Theodore Swanson (NASA GSFC). The Norse settlements in Greenland in the Middle Ages were never robust and eventually failed, with interesting analogies to our movement into the far more hostile environment of space. Such studies remind us of the contribution cross-disciplinary studies can have as we contemplate the potential long-term spread of our species off-planet (preprint here). Thanks to Paul Titze for updates on this conference.
Space Survey Goes Online
Space Expectations is an online survey by the International Academy of Astronautics whose goal is to “Enable a merging of the technological/scientific goals of space activities within society’s expectations. This will lead to programs that are supported by the public, generate more interests and have fewer disconnects with society.” Every completed survey helps as we try to build better bridges between the space community and the public, hoping to muster support for continuing exploration in tough economic times. Your participation is welcome.
by Paul Gilster | Feb 21, 2009 | Culture and Society |
The 91st Carnival of Space offers up Brian Wang’s look at Project Orion, with links to photos and videos relating to nuclear pulse propulsion, one of which I embed here from the This is Rocket Science site. For those who like to take potentially workable ideas up to gigantic scales, Brian discusses the Super-Orion, all eight million tons of it, with the capacity to take three million tons of cargo anywhere in the Solar System.
The pusher plate would have reached a diameter of 400 meters. Brian notes the scale:
400 meters in diameter means that the area (footprint) is about 30 football fields. 4 football fields long by 8 football fields wide. The height of the super-orion is about the height of skyscraper like Taipei 101 or Petronas Towers. The base of the Great Pyramid forms a nearly perfect square with about 230 m (756 feet) on a side. When newly completed, the Great Pyramid rose 146.7 m (481.4 ft)—nearly 50 stories high. Super-Orion would have had the volume of about 10 Great Pyramids.
And don’t miss Bob Nichol’s first post on the Galaxy Zoo blog as the project moves on to its second phase, Galaxy Zoo 2. The new project already has two million galaxy classifications in hand, a remarkable piece of work for this Internet-based program, which uses input from volunteers to classify galaxy types. Says Nichol:
That is staggering for us astronomers as we are usually expect our experiments to take a lot longer. For example, if one wants to use a telescope to study something in the sky, one must write a proposal 6 months in advance, submit it for scrutiny, and then await your allocation of time on a telescope. The process can take nearly a year and then after your night staring at the stars, it can take a further year to analyse the data (assuming it wasn’t cloudy!). Only then are we ready to ask questions of the data and test our observations against our original hypothesis written two years ago in a haste!
Yes, and now the Galaxy Zoo is showing how things happen on Internet time. How we continue to use it, and the new uses we find for it as we go along, will be a major story in itself in terms of how we get science done. I like Nichol’s comment that asking ‘how many galaxies have a bar through the middle?’ is the kind of question that would once have required a career to answer, using the services of grad students to do the grunt work. Now we build the data sets in days. The more venerable among us can remember when CCDs seemed like a revolution. Now they’re only part of the digital reality of a newly enhanced astrophysics.
by Paul Gilster | Feb 20, 2009 | Exoplanetary Science, Missions |
The Kepler launch is coming up on March 5, marking the first time we will have the ability to find a true Earth analogue around another star; i.e., a planet of about Earth’s mass in the habitable zone where water can exist in liquid form on the surface. Which is not to say that COROT may not come close, though Kepler’s enormous star-field (100,000 targets in the Cygnus-Lyra region) and incredibly sensitive camera — a 95-megapixel array of charged coupled devices (CCDs) — is optimized for planets down to Earth size rather than larger ‘super-Earths.’
Image (click to enlarge): Kepler’s target region, the Milky Way ni the Cygnus region, with the instrument’s field of view superimposed. Each rectangle indicates the specific region of the sky covered by each CCD element of the Kepler photometer. There are a total of 42 CCD elements in pairs, each pair comprising a square. Credit: NASA/Carter Roberts (1946-2008).
We just looked at Alan Boss’ remarkable statement that there could be 100 billion trillion Earth-like planets in the visible universe. It’s startling to think that a mission to be launched within weeks could so quickly give us a chance to size up the idea. The thinking is that dozens of planets like ours in the habitable zone should be visible to Kepler if such worlds are common, but if it comes up short, with few or none, we’re going to quickly re-evaluate how unusual a world we live on. A null result would be striking indeed.
William Borucki, who is science principal investigator on the mission, has this to say:
“Finding that most stars have Earths implies that the conditions that support the development of life could be common throughout our galaxy. Finding few or no Earths indicates that we might be alone.”
But let’s get more specific about terrestrial, as opposed to gas giant planets. The Kepler site posts its own numbers, assuming only orbits with four transits in 3.5 years (the mission duration), and assuming that such planets are common around other stars. Kepler should find fifty terrestrial planets in one-year orbits if most are roughly the size of the Earth, and about 185 planets if most are roughly 1.3 the size of Earth’s radius. The number goes up to 640 if most such planets have a size of 2.2 Earth radii, and goes substantially higher still if orbits ranging from a few days to more than a year are considered.
Kepler is looking for transits in those systems where planets cross in front of their stars as seen from Earth, using an instrument that can detect brightness changes of twenty parts per million. After launch, the spacecraft will undergo a two-month checkout as it achieves its Earth-trailing orbit around the Sun. Eventually, Kepler’s science data will be sent to NASA’s Deep Space Network on a monthly basis, with data analysis performed at Ames Research Center in California. We’re obviously going to have much to say about Kepler in coming months.
by Paul Gilster | Feb 19, 2009 | Asteroid and Comet Deflection |
I love it when we find uses for instruments that they were never intended for. In deep space terms, we can go back to Voyager 2, which carried a plasma wave instrument that was designed to measure the charged particles inside the magnetic fields of the gas giant planets it would pass. Voyager 2 was able to tell us much about dust impacts on a fast-moving spacecraft when it was realized that the plasma wave instrument would be able to sense the plasma created by vaporized particles. In other words, the instrument became a de facto dust detection device.
Now I see that the two STEREO spacecraft may be pressed into service to study what’s lurking in the L4 and L5 Lagrangian points, each 150 million kilometers from Earth, with L4 60 degrees in front of our planet and L5 60 degrees behind. Balancing the gravitational field of the Sun with that of Earth, the Lagrange points are interesting places, possibly a junkyard of debris from the early Solar System. It’s known that such points appear around other planets, as witness the thousand or so asteroids that make up the Trojans at Jupiter’s L4 and L5 points.
Image: Relative positions of both STEREO spacecraft, also showing the SOHO and ACE spacecraft. Credit: NASA/Solar TErrestrial RElations Observatory team.
Launched in 2006, the STEREO spacecraft were designed to monitor solar storm activity, one of them moving ahead of the Earth in its orbit, the other behind. But as they gradually move through L4 and L5, their heliospheric imagers can be put to work looking for asteroids. New Scientist has just run a story on the prospect, going on to speculate on an audacious idea put forth by Richard Gott (Princeton), who believes a whole population of objects may be found in these intriguing areas.
Addendum: The statement above turns out to be in error. The concept actually originated with Edward Belbruno at Princeton, and resulted in a paper for which he was lead author. That paper is Belbruno, “Where Did The Moon Come From?” Astronomical Journal, Vol. 129, No. 3 (March 2005), pp. 1724-1745 (available online). Dr. Gott was co-author on this work.
Gott wonders whether a large object of the sort believed to have struck the Earth some four billion years ago, thus creating the Moon, may have grown up close by, gradually nudged out of one of the Lagrangian points into collision with our planet. It’s worth considering, since as the New Scientist article points out, an incoming Mars-sized object from elsewhere in the Solar System would have struck the Earth with so much energy that it would have destroyed it. That and the makeup of oxygen isotopes found on the Moon — the same as on Earth — hints that the impactor must have formed in nearby space. From the article:
Gott thinks that any objects still in L4 and L5 may be leftovers from the formation of that impacting body. “Let’s say that you find a number of objects there. In that case, they would be great targets for a sample-return mission to see if they had the same oxygen isotope abundances as Earth,” says Gott. If they do, Gott believes this strengthens the case for the Earth-impactor to have formed there.
Back to that dust issue — the STEREO vehicles have been seeing a wide variety in dust impacts, from just a few up to several thousand per day. What will STEREO’s heliospheric imagers find at the L4 and L5 points? Earth-based telescopes have yet to find asteroids there, so the current thinking is that any that do lurk in the regions are small, less than a kilometer across. But if Gott is right, even a few lucky finds could be fodder for a future mission, one that would give us new insight into the early history of the Solar System.
by Paul Gilster | Feb 18, 2009 | Astrobiology and SETI |
Just how many forms of life are there? We often speculate here about life on other worlds, but Paul Davies (Arizona State) is currently exploring the question from a different perspective entirely. Davies would like to know whether a ‘second genesis’ might have occurred, producing a fundamentally different form of life that would have evolved right here on Earth and might still occupy our planet. Life may, in other words, have started many times, perhaps with significantly different results we just haven’t uncovered yet.
Call it a ‘shadow biosphere,’ a concept the physicist calls for exploring:
“…[It] is still just a theory. If someone discovers shadow life or weird life it will be the biggest sensation in biology since Darwin. We are simply saying, ‘Why not let’s take a look for it?’ It doesn’t cost much (compared to looking for weird life on Mars, say), and, it might be right under our noses.”
Finding these alternate life forms, if they exist, may be tricky, as they could be lurking in places where conditions are extreme, such as deep sea hydrothermal vents, salt lakes or areas high in ultraviolet radiation. And as Davies told a symposium at the AAAS annual meeting in Chicago, our assumptions about biochemistry may be getting in the way of our finding life in the shadow biosphere. “We don’t quite know how weird life would look. It’s as wide as the imagination and that’s why it’s really hard to look for.”
That last quote comes from a BBC story on the possibilities of alien life forms on Earth. The question Davies is asking is profound, for if life did get its start multiple times on our planet, we can assume it’s far more likely to have appeared elsewhere in the universe. The case for life on those trillions of habitable planets Alan Boss talks about in yesterday’s entry becomes more and more formidable. The BBC story cited above also discusses the work of Steven Benner (University of Florida), whose team has created what Benner calls “…an artificial synthetic chemical system capable of Darwinian evolution.”
Benner says the molecule — a modified version of the DNA double helix but with a six-letter genetic alphabet instead of four — is not self-sustaining (“You have to have a graduate student stand there and feed it from time to time”), but it is evolving. He wants to apply natural selection to it to watch it evolve under selective pressure. So is Benner’s creation alive, or are we basing too much on our Earth-based assumptions? “Remember – just because you are a chemical system which is self-sustaining and capable of Darwinian evolution, that doesn’t mean that is the universal definition of life,” the scientist adds.
A useful caveat. The question that hovers over our first encounter with truly alien life, assuming it is out there, is not what we’ll say to it as much as whether or not we’ll even recognize it as life. Last April I quoted Jacob Bronowski on this in a statement from The Ascent of Man that bears repeating:
“Were the chemicals here on Earth at the time when life began unique to us? We used to think so. But the most recent evidence is different. Within the last few years there have been found in the interstellar spaces the spectral traces of molecules which we never thought could be formed out in those frigid regions: hydrogen cyanide, cyano acetylene, formaldehyde. These are molecules which we had not supposed to exist elsewhere than on Earth. It may turn out that life had more varied beginnings and has more varied forms. And it does not at all follow that the evolutionary path which life (if we discover it) took elsewhere must resemble ours. It does not even follow that we shall recognise it as life — or that it will recognise us.”
As to Davies, I’m looking forward to this prolific author’s next book. The Eerie Silence, scheduled for publication next year, is to be a new look at SETI and its dilemmas. Davies wrote up the ‘weird life’ concept in “Are Aliens Among Us?” Scientific American Vol. 297; No. 6, pp. 36-43 (available online). Thanks to Dave Moore for the tip on this story.
