On Deflecting Near Earth Objects

The B612 Foundation continues to examine the danger of near-Earth objects (NEOs). As noted earlier in these pages, B612 points to the continuing evidence for asteroid and comet impacts and their role in shaping the planet's history; the much discussed demise of the dinosaurs, due to a likely asteroid strike in the Yucatan, is but one of the instances where the planetary ecology has been altered. We know that the Earth orbits in a swarm of near-Earth asteroids, with a probability of collision in this century that the Foundation pegs at an unacceptably high 2 percent. Given these concerns, and the possible dangers posed by the object called NEO 99942 Apophis, the Foundation has engaged in a dialogue with NASA about possible missions to this asteroid. Apophis (also known as 2004 MN4) is on course for a near-miss in 2029 , with the 400-meter asteroid approaching to within 32,000 kilometers. What happens afterwards as the near-miss itself disrupts the orbit of this object remains a...

read more

Robert Goddard on Interstellar Migration

"A manuscript I wrote on January 14, 1918 ... and deposited in a friend's safe ... speculated as to the last migration of the human race, as consisting of a number of expeditions sent out into the regions of thickly distributed stars, taking in a condensed form all the knowledge of the race, using either atomic energy or hydrogen, oxygen and solar energy... [It] was contained in an inner envelope which suggested that the writing inside should be read only by an optimist." -- Robert Goddard, "Material for an Autobiography," (1927), available in Pendray, G. E. and Goddard, E. C. (Eds.), The Papers of Robert H. Goddard (New York: McGraw Hill, 1970).

read more

Photon Pressure Affects Japanese Spacecraft

The Japanese spacecraft Hayabusa, now in a 'parking orbit' above the asteroid Itokawa, is providing good evidence of just how useful the pressure of solar photons can be. Japan's Institute of Space and Aeronautical Science (ISAS) reports that the force being experienced by the spacecraft is 1/100th of the thrust produced by its ion engines, but fully ten times larger than the gravity of Itokawa itself. The effect is consequential enough that it must be factored into Hayabusa's descent close to Itokawa's surface; the spacecraft will deploy a small surface 'hopper' called MINERVA to take measurements on the asteroid. Hayabusa (once known as MUSES-C and renamed for a Japanese rocket pioneer) thus becomes both a testbed for current technologies and a reminder of a future one. Its electric propulsion or ion drive engines have met the challenge of asteroid rendezvous, although their performance was degraded by solar panel damage from solar flares in 2003. The spacecraft also carries an...

read more

A Gravitational Lens at Work

Gravitational lenses of the sort discussed in yesterday's post are now widely discussed. The idea that gravity can bend light may seem counterintuitive but we've seen numerous demonstrations of the effect, starting with the famous eclipse studied by Arthur Eddington in 1919. Hoping to test Einstein's general theory of relativity, Eddington traveled to the island of Principe, off the coast of West Africa. There, despite initially cloudy skies, he was able to take the crucial photograph that verified Einstein. Stars in the Hyades Cluster that should have been blocked by the Sun were revealed in the image, offset by an amount close to that predicted by Einstein. Some have questioned whether Eddington's equipment was sufficiently precise to make accurate readings, but whatever the case, the bending of light as a result of gravity has stood up. Among the various images that show this effect in deep space, none is as dramatic as the one below. Here we're looking at multiple bluish images...

read more

A Mission to the Gravity Focus

Voyager 1 is, in a sense, our first interstellar spacecraft, with evidence mounting that it has reached the heliopause, that area marking the boundary between the Sun's outward-flowing particles and the true interstellar medium. The New Horizons mission, scheduled for launch in January, will go on to explore at least part of the Kuiper Belt. But what will our first true interstellar mission be; i.e., when will we launch a spacecraft designed from top down to studying nearby interstellar space? The answer may well be a mission to the Sun's gravity focus. Located at 550 AU (3.17 light days), some 14 times farther from the Sun than Pluto, the focus is that point to which the Sun's gravity bends the light from objects on the other side of it. The effect is to magnify distant images in ways that could be observed using the proper equipment. The effect of gravitational focus, first studied by Einstein in 1936, had already borne observational fruit by 1978 in the discovery of a 'twin...

read more

Deep Space Transmission Strategies

One reason we need to re-think our communications strategies is that our resources are so limited. The Interplanetary Internet Project, for example, points out as a major justification for its work that if we can network spacecraft in distant planetary environments, we can sharply cut back on the amount of antenna time needed. After all, having a trio of spacecraft (including an orbiter, perhaps, and two rovers) linking their data to a single relay would mean a unified data download to Earth. The IPN idea would create new networking protocols that could make these things happen. But research continues on other fronts, including the technology we use to transmit signals. An upcoming paper discusses phased arrays, wherein a large number of mini-transmitters could send a combined beam into the sky. Systems like these are familiar to those working with military radar but have been hitherto unavailable for cost reasons for civilian uses. The paper, by Louis Scheffer at Cadence Design...

read more

The Best Way to View Terrestrial Worlds

Centauri Dreams has been a champion of Webster Cash's New Worlds Imager for several years now. The proposal, whose initial study was funded by NASA's Institute for Advanced Concepts, offered a way to find terrestrial planets around other stars and, in its most fully developed configuration, to create startlingly sharp images of such worlds down to the level of continents and weather patterns moving across their surfaces. Now two new developments -- related in a phone call from Cash last week -- bring New Worlds Imager to the fore as NASA weighs strategies for its Terrestrial Planet Finder mission. First, Cash has changed the basic design of New Worlds Imager to move away from the enormous 'pinhole camera' concept discussed earlier in these pages to an occulter -- a design that blocks the starlight from the central star to allow its planetary companions to be visible. The problem with occulters has always been that no matter how scientists worked with their design, they could not get...

read more

Brown Dwarfs May Have Planets

If brown dwarfs, those 'failed stars' that never make it to the stage of full nuclear burning, can have planets around them, then the speculations of Karl Schroeder's novel Permanence (New York: Tor Books, 2002) may be closer to reality than Centauri Dreams once thought. Schroeder imagines human colonies, artificially sustained through extraordinary technologies, on planets surrounding a variety of brown dwarf stars, an entire civilization of humans living in the spaces between the 'lit' stars we see in the night sky. Now the Spitzer Space Telescope has found the signs of early planet formation around six young brown dwarfs located some 520 light years away in the Chameleon constellation. Ranging in size from between 40 to 70 times the mass of Jupiter, the brown dwarfs are between 1 and 3 million years old. And five of them have disks made up of dust particles that are clearly sticking together, in what looks suspiciously like the early stages of planet formation. The astronomers...

read more

SETI and Drake: Part II

Yesterday we looked at Milan ?irkovi?'s paper “The Temporal Aspect of the Drake Equation and SETI" (Astrobiology Vol. 4 No. 2, pp. 225-231), and pondered whether there might not be a 'communications window' -- an interval for any society between when it reaches the technological capacity for interstellar communication and the point when it becomes a 'supercivilization' unlikely to use conventional SETI methods to contact us or anyone else. If so, that 'window' would have a profound effect on how many civilizations we might be able to contact via SETI, and would thus change our answers to the Drake Equation. But there are other kinds of assumptions built into the equation that may be problematic. ?irkovi? notes that the equation assumes a more or less uniform physical and chemical history of our galaxy, but uniformitarianism doesn't work well in astrophysics or cosmology (think of the Steady State theory -- uniformitarian -- vs. the Big Bang, which introduced the concept of epochs...

read more

A Hard Look at SETI and the Drake Equation

The famous Drake Equation was developed as a way to estimate how many technological civilizations might exist and thereby be targets for SETI research. Conceived in 1961 as astronomer Frank Drake worked at the National Radio Astronomy Observatory (Green Bank, WV), the equation exists in a variety of forms depending on which authors you consult (see, for example, this SETI Institute discussion of the equation). But all variants draw on the same idea: to study extraterrestrial civilizations, you must consider such factors as: the mean rate of star formation in the Galaxy; the fraction of stars that can support life; the fraction of stars that have planetary systems; the number of planets per system with conditions suitable for life; the number of planets where life does originate and evolve; the fraction of planets where intelligent life forms develop; the fraction of planets where intelligent life develops technology; and a final, crucial measure: the mean lifetime of a technological...

read more

New Horizons Readied for Flight

With liftoff scheduled for January, the New Horizons mission to Pluto and Charon (and, if we are lucky, at least one flyby of a more distant Kuiper Belt object) continues to generate excitement in the scientific community. The spacecraft is now at the Kennedy Space Center and will be moved to the launch pad in December, with liftoff planned for January 11. Major testing on the science payload is complete. The next round of major instrument calibrations and testing won't occur until the early months of the journey as New Horizons moves toward a 2007 flyby of Jupiter for a gravity assist to Pluto. How do you package enough instrumentation for good science at the edge of the Solar System into a payload that draws only 28 watts of power? The science payload work was led by the Southwest Research Institute (SwRI), whose recent news release lists the seven instruments that will explore these icy worlds: Alice, an ultraviolet imaging spectrometer that will probe the atmospheric composition...

read more

A Multi-Tiered Approach to Planetary Exploration

As we saw in yesterday's post on microbots, one of the problems of robotic exploration is that we put our equipment into relatively smooth terrain. That makes sense, given the time and cost of getting rovers to Mars, for example; what a shame it would be to see a priceless instrument package slam into a mountainside as it touches down. But rugged terrains, those places where water and volcanic activity have changed a landscape, may tell us much about a planet's history and the possible existence of life on it. Now a team of scientists is proposing a fundamental change to our existing paradigm of robotic exploration. In addition to orbiters, the team (scientists from the California Institute of Technology, the University of Arizona, and the U.S. Geological Survey) has focused on airborne instrument packages (think 'blimps'), complemented by the kind of small, robotic explorers that could work their way into even the most hostile landscapes. "We're not trying to take anything away from...

read more

Surface Exploration by Microbot

One way to explore a planetary surface is by rover, much as we are doing now on Mars with Spirit and Opportunity. The amount of data we've received from these missions has been nothing short of sensational, but as we look to the future, a key problem looms: rovers can sample only small areas of the surface. They're a precious commodity that has to be targeted to high-value destinations, meaning they're not adaptable to broad, general surveys. But a new robotic approach may come to the rescue, and it's one that has just received Phase II funding from NASA's Institute for Advanced Concepts. Under the supervision of principal investigator Steven Dubowsky (Massachusetts Institute of Technology), the work focuses on 'microbots' to enable large-scale explorations. Microbots are spherical robots that could be dropped by the thousands, perhaps through air-bags deployed from orbiter spacecraft. They would be able to hop, bounce and roll their way to sites in the most rugged terrain, equipped...

read more

Viewing Continents on Distant Worlds

It was in 1999 that former NASA administrator Dan Goldin spoke to the American Astronomical Society about what future telescopes might be able to see around distant stars. He imagined a classroom filled with images of exoplanets. "When you look on the walls, you see a dozen maps detailing the features of Earth-like planets orbiting neighboring stars," Goldin said. "Schoolchildren can study the geography, oceans, and continents of other planets and imagine their exotic environments, just as we studied the Earth and wondered about exotic sounding places like Banghok and Istanbul . . . or, in my case growing up in the Bronx, exotic far-away places like Brooklyn." Is a telescope that could take such pictures remotely conceivable? The most innovative proposal I've heard to achieve these goals is Webster Cash's New Worlds Imager concept. The University of Colorado at Boulder astronomer knows how tricky the project would be. As astronomer looking at the Earth from Alpha Centauri would face...

read more

Via Nanotechnology to the Stars

What a pleasure to discover that Robert Freitas' Kinematic Self-Replicating Machines is now available online. The 2004 book (from Landes Bioscience of Georgetown TX) is the most comprehensive study of nanotechnology yet written, a compendium of information on self-replicating systems both proposed and experimentally studied. Moreover, it contains a survey of the historical development of nanotechnology, 200 illustrations and over 3000 references to the technical literature. That nanotechnology (and self-replicating systems in particular) could change our ideas of interstellar flight now seems obvious, but not so long ago ago the concept of one machine building another was studied only at the macro-level. Thus Freitas' previous work on a self-reproducing spacecraft he called REPRO. The scientist wrote the concept up in a 1980 issue of the Journal of the British Interplanetary Society, conceiving of a mammoth Daedalus-style spacecraft built in orbit around Jupiter and, like Daedalus,...

read more

Changes at Centauri Dreams

When I began the Centauri Dreams site in August of 2004, the motivation was utilitarian. I was looking for a way to keep up with ongoing research into deep space exploration, figuring it would be helpful to establish a site that followed news day by day and maintained it in a searchable archive. Centauri Dreams the Web site actually preceded my book of the same name by several months, and it was in the back of my mind to use research collected at the site in future writing projects. That motivation still exists. But something else happened in the intervening months. As readership grew, I found I was making new contacts in the research community, not just in the government agencies like NASA and ESA, but also in academic environments and commercial companies. Those contacts have been priceless, and have led to some fine friendships. And they've kept my eye on the main prize, which in my judgment is to put deep space research into the broader context of society's awareness of time. To...

read more

Life’s Origins in the Cosmos

To make life happen you need organic molecules that contain nitrogen. Now new work at NASA's Ames Research Center, to be reported in the October 10 issue of the Astrophysical Journal, reveals that organic molecules found throughout the galaxy do, in fact, contain nitrogen. "Our work shows a class of compounds that is critical to biochemistry is prevalent throughout the universe," said Douglas Hudgins, an astronomer at NASA Ames and principal author of the study. The studies combined laboratory experiments and computer simulations. We already knew, thanks to the Spitzer Space Telescope, that complex organic molecules called polycyclic aromatic hydrocarbons (PAHs) are all but ubiquitous. Learning that PAHs contain nitrogen implies that the building blocks of life are seeded everywhere in the universe. From a NASA Ames news release, quoting astrochemist and team member Louis Allamandola: "Chlorophyll, the substance that enables photosynthesis in plants, is a good example of this class...

read more

Studying the Atmosphere of Terrestrial Exoplanets

Of the 161 planets so far detected around other stars, eight have been discovered by the transit method as they moved between that star and the line of sight to Earth. Such transits, effective as planet finders in themselves, are also useful because they allow scientists to study the properties of the atmospheres around these worlds. The first planet found by transit methods orbits the star HD 209458 and is the object of intense atmospheric study. Can such methods be applied to transiting Earth-size planets? A new paper studies the question in terms of the kind of signatures that might be expected, and the near-term technologies that could make such detections possible. The paper focuses on terrestrial worlds orbiting K, G or F-type stars, and notes that the best targets will be K-type stars, which are in any case more abundant than the other types as well as smaller. According to the analysis, the strongest signatures in the atmosphere of such worlds could be water, ozone and carbon...

read more

Refining the Tools for Life Detection

If you're looking for a terrestrial analogue to one part of the Martian environment, you could do worse than the ice vents inside a frozen volcano on the Norwegian island of Svalbard. There, in a one million year old volcano called Sverrefjell, a team of researchers has found a community of microbes both living and fossilized. Ice-filled volcanic vents are believed to occur on Mars and may well be a potential habitat for life on the planet. Behind the Svalbard investigations is AMASE, the Arctic Mars Analog Svalbard Expedition, which is designing devices and techniques that may one day be used by automated landers to search for life on Mars. And thus far the findings are promising. The team has been able to perform its tests while maintaining scrupulous sterility, a key factor in ensuring that 'life' detections on another planet aren't simply the result of Earthly microorganisms being introduced into the local ecology. Examining 780-million year old sedinmentary rocks, the team also...

read more

Bright Spot on Titan Still a Mystery

What is that bright 300-mile wide patch on Xanadu, the continent-sized region on Titan, that Cassini noted last March? The area outshines everything else on the moon in long infrared wavelengths (it's described as "...spectacularly bright at 5-micron wavelengths..."), and after considerable investigation does not appear to be a cloud, a mountain or a geologically active hot spot. In visible light, Cassini saw a bright arc-shaped feature of approximately the same size in late 2004 and again in 2005. Image: Combined VIMS and ISS images of Titan's mysterious bright red spot gives researchers more information about the feature than either single view. (Credit: NASA/JPL/University of Arizona/Space Science Institute). That quotation above comes from a University of Arizona news release, one that goes on to note that subsequent radar imaging found no real temperature variation between the spot and the terrain around it. That rules out the possibility of an active ice volcano, and quickly...

read more

Charter

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

Now Reading

Recent Posts

On Comments

If you'd like to submit a comment for possible publication on Centauri Dreams, I will be glad to consider it. The primary criterion is that comments contribute meaningfully to the debate. Among other criteria for selection: Comments must be on topic, directly related to the post in question, must use appropriate language, and must not be abusive to others. Civility counts. In addition, a valid email address is required for a comment to be considered. Centauri Dreams is emphatically not a soapbox for political or religious views submitted by individuals or organizations. A long form of the policy can be viewed on the Administrative page. The short form is this: If your comment is not on topic and respectful to others, I'm probably not going to run it.

Follow with RSS or E-Mail

RSS
Follow by Email

Follow by E-Mail

Get new posts by email:

Advanced Propulsion Research

Beginning and End

Archives