A new study suggests that close-in gas giants may heat up electrically like toaster coils plugged into their host stars via the power lines of the stellar wind — explaining why the planets inflate.

In a study presented at the meeting of the American Astronomical Society last week in Indianapolis, astronomer Derek Buzasi (Florida Gulf Coast University) proposes that hot Jupiters are like toasters.

To be precise, his modeling suggests that these planets are heated by an electric current running deep through the planet's interior. It's plugged into an external power source — the host star. The interplanetary power supply would offer a new solution to a mystery that has vexed astronomers for over a decade.

Since 2000, transit observations have allowed astronomers to directly measure the sizes of exoplanets based on how much light they block as they pass in front of their host star. These measurements have revealed that gas giants close to their host stars are "inflated" — larger in size than a planet of the same mass further away. A 2011 study of data from NASA's Kepler telescope by Brice-Olivier Demory and Sara Seager (Massachusetts Institute of Technology) found that hot Jupiters have a baseline average radius of around 87% that of Jupiter. But when the planets orbit closer in and the incoming energy from the host stars reach about 150 times what Earth receives, the planets begin to puff up. Around a star like the Sun, this is at 0.08 AU, or about 1/4 the distance of Mercury's orbit.

But why? Atmospheric-heating models can currently account for only some of the inflation trend, says Adam Burrows (Princeton), who is not involved with Buzasi's study. These models incorporate the planet's mass, its composition, distance from the star, and the star's type and age. Due to the intense radiation of its star, "the [planet] sizes could be up to 1.3 Jupiter radii quite easily," says Burrows. But a handful of hot Jupiters — "WASP-19, WASP-12, TrES-4b," he rattles off — are inflated far beyond any model, some nearly twice the radius of Jupiter.

Toasters Among Us

Astronomers have proposed a variety of extra heat sources for the deep interior that could puff up these planets. For example, observations show that giant-planet host stars are composed of more heavy elements than our Sun; perhaps, proposed a team led by Burrows in 2007, the hot Jupiters also have heavier makeups that absorb more incoming energy than current models predict. And in 2010, a Caltech duo (Konstantin Batygin and David J. Stevenson) suggested that the supersonic winds in a hot Jupiter could generate a significant heating current as ions in the atmosphere streak across the planet's magnetic field at up to 1 km per second (2,200 mph). Most promisingly, tidal heating due to gravitational interaction with the star (and perhaps other planets) could heat the inside of a hot Jupiter directly.

Buzasi’s solution invokes the magnetic field of the star. In our solar system the Sun is like a power station: its winds of charged particles are interplanetary power lines, carrying current through the solar system. That current links up with the Earth's magnetic field at its poles, where it penetrates into the ionosphere, the layer of charged particles ionized by the Sun at altitudes of hundreds of kilometers. Combined with thunderstorm action, this creates a global electric circuit, driving a weak current flowing high above Earth's magnetic poles.

Now apply this model to a gas giant whizzing around its star in a close orbit, and the planet heats up to around 1,400K (2,060°F). It also becomes a much better conductor, more like a metal, as its atoms ionize. Buzasi calculates this current is much stronger and penetrates into the interior of the planet itself, where the pressure is thousands of times that of Earth's atmosphere.

"Instead of having thousands of amps and a hundred thousand volts [as on Earth], we have millions of volts and billions of amps," said Buzasi at a press conference Tuesday. It turns out that the interplanetary electric grid can provide enough energy to heat — and inflate — the planet, like a toaster plugged into its star.

How To Spot a Toaster

So is there any observational evidence? Buzasi says one piece comes from the Kepler database. Of the hot Jupiters that Kepler has found, the inflated ones exist only around highly active stars, hinting that magnetic activity and a strong stellar wind are involved. Another "suggestive" observation, Buzasi writes in his study, is that the 0.08 a.u. cutoff, closer than which hot Jupiters begin to inflate, "roughly corresponds to the Alfvén radius for the Sun," where the solar wind begins to dominate over the Sun's magnetic field.

Burrows doesn't like invoking an arbitrary threshold because he says some of the inflation trend can be explained by models without an extra heat source. He says he isn't yet "wedded to any particular model" — even his own. But he finds Buzasi's model "interesting" and says it "deserves further consideration" because it provides a way for the current to close deep inside the planet. "The depth at which you deposit the heat is rather crucial," says Burrows. "The deeper you put this heat, the more effect it has."

Burrows says more statistics would help convince him. "For example, for stars that are the same but have a higher level of [magnetic] activity, do you get a larger radius for the planets?" he wonders.

Buzasi noted one way that the effect could be directly confirmed: the interplanetary magnetic field should induce aurora, which could be observed in the radio or UV. "If the planet has any kind of magnetic field, those have to be very powerful."

NASA’s Swift satellite produces spectacular ultraviolet images of the Small and Large Magellanic Clouds.


Spectacular high-resolution images released this week at the 222nd American Astronomical Society conference in Indianapolis reveal two of the Milky Way’s nearest galactic neighbors in a new light. The images, presented by Stefan Immler (NASA Goddard Space Flight Center), are gigantic mosaics of the Small and Large Magellanic Clouds (SMC and LMC, respectively).

Immler and his colleagues observed the dwarf galaxies in the ultraviolet 160 to 330 nanometer range using the Ultraviolet/Optical Telescope (UVOT) aboard NASA’s Swift satellite, which launched in November 2004. Though Swift is known for hunting gamma-ray bursts, its UV capabilities also make it useful for other projects. By surveying galaxies in the UV, astronomers can study young stars and star-forming regions, which are brighter in this wavelength range than Sun-like stars.

The composite images reveal a less uniform galactic structure than appears in visible-light images, as shown in the animation above. Since visible-light images can’t separate the light from the galaxies’ individual stars, it is nearly impossible to isolate stellar populations and determine their distributions throughout galaxies. However, UV images provide an unobstructed view of individual young stars. The LMC image highlights the lively star formation in and around the Tarantula Nebula, home of SN 1987A, the first naked-eye supernova in modern times.

More Than A Pretty Picture

The Small and Large Magellanic Clouds are particularly interesting to astronomers because they are among the closest galaxies to us: the LMC lies about 163,000 light-years from the Sun and the SMC about 200,000 light-years. In comparison, the familiar Andromeda Galaxy is 2.5 million light-years away. Although these galaxies are small relative to the Milky Way, they are so close to us that they exceed the UVOT’s 17-square-arcminute field of view. To create a composite image for each galaxy, astronomers stitched together 2,200 snapshots of the LMC and 656 of the SMC. Both images have resolutions of 2.5 arcseconds, the equivalent of seeing a dime from a mile away.

Since the Magellanic Clouds contain so many hot, luminous young stars, they are excellent grounds to study stellar evolution. The images reveal 250,000 ultraviolet sources in the SMC and 1 million in the LMC, and already Immler and his colleagues are discovering unusual results. Preliminary analyses reveal thousands of massive stars (more than 10 times the mass of the Sun) and some highly exotic stars that they didn’t expect would emit such large amounts of UV.

The new surveys will be used to construct age maps for the galaxies, as well as to investigate how much observed light is dimmed by intervening dusty clouds in different parts of the galaxies.

The images will later be made available to interested scientists and students as part of a “legacy” project, but, for now, you can see more images in the NASA press release. Below, you’ll also find a video narrated by Immler describing what the images reveal.

Its tests and calibrations complete, NASA's Curiosity rover will soon switch to a long-distance mode to reach its main objective — a towering mound of layered sediments — several months from now.

Have you ever dashed off to the grocery store, planning to just grab some milk and eggs, and then you get sidetracked by all the tempting fresh fruit and bakery goodies?

That's basically the situation mission scientists for NASA's Mars Science Laboratory (MSL) find themselves in. It's been 10 months since Curiosity touched down inside Gale crater. The rover's ultimate destination is Aeolis Mons (widely known as "Mount Sharp"), a massive mound that rises 3 miles (5 km) high from the crater's broad floor. This stack of layered sediments likely holds the key to why, when, and how Mars morphed from a clement world gurgling with liquid water in its youth to the stark, frigid, and inhospitable place it is today.

But Curiosity isn't there yet — and likely won't arrive until next year. For the past six months, the rover has been poking around "Glenelg," an area no bigger than a football field with many intriguing geologic outcrops. Since Curiosity is more capable — and more complicated — than any previous interplanetary lander, its handlers have been executing a carefully paced sequence of operations to test all the instruments and mechanisms thoroughly.

Last February ground controllers commanded the craft to drill into an exposure of soft mudstone nicknamed "John Klein." A month later, after instruments had analyzed finely powdered samples of the tailings, scientists reported that this rock contains abundant smectite, a group of clay-like minerals that forms in the presence of water. Also, the presence of calcium sulfates imply that the water probably had a relatively neutral pH and was not strongly salty. It was all good news on the habitability checklist.

Last month Curiosity drilled into a second outcrop, called "Cumberland", then fired its ChemCam laser several times to analyze the powdered tailings. Everything went smoothly, though the analysis of the elements and minerals those contain is ongoing.

But no further drilling is planned before Curiosity starts rolling in earnest. In a few weeks engineers will shift gears to a distance-driving mode that covers more ground and involves fewer sightseeing stops, since the big mound's lower slopes lie about 5 miles (8 km) to the southwest.

The roving geology laboratory would have wrapped up its work in Glenelg sooner, but there were two delays. Earlier this year an electronic glitch halted science activities for about a month, and then communications were suspended for a few weeks when Mars passed very near the Sun as seen from Earth.

"The trip to the Glenelg region has been well worth it," says Joy Crisp, MSL's deputy project scientist at the Jet Propulsion Laboratory. "The science team is very pleased with the results that we've gotten."

"We don't know when we'll get to Mount Sharp," comments project manager Jim Erickson in a NASA press release issued Wednesday. "This truly is a mission of exploration." He speculates that it'll take at least 10 months to a year — and that assumes no sightseeing along the way. Yet even now the mission's scientists and engineers are compiling a list of choice spots that they'll have the rover check out in the months ahead.

New observations with the powerful ALMA observatory reveal a huge pile-up of dust around a young star.

Our understanding of planet formation is limited to snapshots of time. Astronomers never directly observe the entire formation of a single exoplanet system; instead, they combine observations of planetary formation around stars of different ages, glimpsing frozen moments in a process that takes millions of years to happen. Thus, there are significant gaps in our understanding of how planets form. We know that dusty disks form around other stars, and that there are young planets carving holes in some of these disks, but the details behind how little dust balls build up into planets like Earth and Jupiter are something of a mystery.

Now, a new result published in this week’s Science may unravel some of that mystery, giving great insight into one of the thorniest problems in the formation process.

Nienke van der Marel (Leiden University, the Netherlands) and an international team of astronomers used the growing Atacama Large Millimeter/submillimeter Array in Chile to observe the young star Oph IRS 48. This star is about twice as massive as the Sun and only about 15 million years old. (These numbers are rough.) It’s also surrounded by a wide disk of dusty gas, with an inner gap reaching out to about 25 Earth-Sun distances from the star. The team traced the distribution of this material with exquisite precision, creating a high-resolution map of the dusty disk’s radio emission.

The insight came when the team compared observations at three different wavelengths. Each wavelength is sensitive to different sizes of dust grains, meaning that the astronomers can track the behavior of multiple types of material in the disk. At a wavelength of 0.44 mm — where dust the size of a grain of sand emits the most light — the team found a large, almost banana-shaped asymmetry near the disk’s inner edge. The other two wavelengths, which were sensitive to molecular gas and smaller dust particles, did not show this asymmetry. The feature spans nearly one-third of the inner rim of the disk and is more than 100 times brighter than the opposite side.

The ALMA observations are the smoking-gun signature of a process that until now was only theoretical: the so-called "dust trap." The dust trap is a mechanism that herds together larger dust grains, keeping them from spiraling in toward the star. Typically, the smaller particles travel with the molecular gas in orbits around the disks of young stars, but drag forces cause larger particles — the exact size depends on the distance from the star — to lose kinetic energy and spiral in. This process should be relatively fast, but since planets are fairly common, many astronomers have put forth theories to explain how dust hangs around long enough to form planets.

Van der Marel’s team thinks the clump of millimeter-size grains might result from the gravitational influence of a massive planet or brown dwarf orbiting in the disk gap around Oph IRS 48. (The planet would also be responsible for clearing that gap in the gas, which serves to slow down the flow of gas and dust onto the star.) The planet’s presence could create a vortex on the disk’s edge, where the pressure in the hurricane-like system acts as a funnel, keeping dust particles trapped and giving them time to coalesce into planetesimals.

That doesn’t explain how the gap-carving planet formed, though. The authors also think it’s unlikely that, so far from the star, this congregation of dust will form a planet. Instead, they suggest that it might be the predecessor of a system similar to our own Kuiper Belt. And since we know that planets are relatively common, there must be other ways to trap dust, in addition to having a relatively massive body already orbiting the star. Either way, the observations by van der Marel and her team are a big step in understanding this mystery.


Reference: N. van der Marel et al. "A Major Asymmetric Dust Trap in a Transition Disk." Science, 7 June 2013.

Galactic cosmic rays and high-energy solar particles, recorded aboard NASA's Curiosity rover during its 8½-month interplanetary cruise, will give future astronauts a significant — but not excessive — dose of radiation on a round-trip journey to Mars.

Ever since Victor Hess discovered cosmic rays in 1912, scientists have come to realize that space radiation is one of the most formidable hazards during long-duration space travel. A typical astronaut aboard the International Space Station, even while protected by the craft's outer hull and Earth's magnetosphere, absorbs as much radiation in a six-month stay as we ground-dwellers do in 20 years. Head deeper into space — say, on a mission to a nearby asteroid or to Mars — and the risks are magnified considerably.

Plenty of craft have monitored space radiation over the years, but those detectors were completely unprotected in order to get "raw" measurements. Now, however, researchers finally have an idea of how much an astronaut would get zapped inside a reasonably well-shielded spacecraft cruising through the inner solar system.

The findings come from the Radiation Assessment Detector (RAD) that took an 8½-month ride to Mars aboard NASA's Curiosity rover. During that long cruise, RAD was installed inside Curiosity, which in turn was sandwiched inside a coccoon-like aeroshell with the rocket-propelled descent stage over it and a thick heat shield below it. This gave RAD shielding from space radiation much like what NASA engineers are building into the forthcoming Orion crew capsule.

Weighing just 3.8 pounds (1.7 kg), the instrument has an upward-looking "telescope" that lets radiation enter through a 60°-wide cone, and it registers hits from two kinds of high-energy particles. There's a constant background of galactic cosmic rays (GCRs), stripped-down nuclei of various atoms, that arrive from the depths of interstellar space at relativistic speeds and can pack a punch of 500 to 600 million electron volts (MeV) or more. The other major source comes from the Sun in the form of high-energy protons, helium ions, and a few heavier ions. Sporadic flares and coronal mass ejections accelerate these solar energetic particles (SEPs) to energies of up to a few hundred MeV. Both types are harmful because they ionize the atoms in any tissue they're passing through.

As reported by Cary Zeitlin (Southwest Research Institute) and others in Science for May 31st, the RAD instrument recorded the equivalent of 0.466 sievert (a unit of measurement for tissue exposure to ionizing radiation) while en route to Mars. Almost all of that came from cosmic rays: although RAD recorded five distinct pulses of SEPs between early December 2011 and mid-July 2012, those accounted for only about 5% of all the particles detected. These results are actually quite close to researchers' previous estimates of radiation exposure.

"In terms of accumulated dose, it's like getting a whole-body CT scan once every five or six days," Zeitlin notes in a SwRI press release. To put this in perspective, NASA draws the line at 1 sievert of accumulated radiation exposure over an astronaut's entire career, a dose that statistically increases the chance of cancer-induced death by 3%.

Based on the RAD results, a round-trip mission to Mars involving about 360 days of interplanetary travel would expose the crew to about 0.6 sievert of radiation. That's a lot of radiation, though under the established lifetime limit.

But predicting the harm from space radiation is an inexact science. For example, the Sun was relatively quiet during Curiosity's long cruise — yet much more potent solar flares can and do occur. Also, women are more susceptible than men to a given radiation dose because they have lower body masses. And no one really knows how much tissue damage the highest-energy cosmic rays can cause, making assumptions about exposure uncertain.

Still, it's progress. "Scientists need to validate theories and models with actual measurements, which RAD is now providing," notes principal investigator Donald Hassler "These measurements will be used to better understand how radiation travels through deep space and how it is affected and changed by the spacecraft structure itself."

Skilled amateur astronomers gathered in California to share their research results.

The annual symposium of the Society for Astronomical Sciences is a busy three days that span the breadth of small-telescope astronomical research. This year’s symposium (May 21-23) touched on planetary science, variable star photometry, spectroscopy (both instruments and project results), astronomical projects for education, and environmental studies — among other things. About 100 people attended the symposium this year.

It isn’t practical to do justice to all the talks that were presented, but here are a few that I found particularly interesting:

Exoplanets around white dwarfs: With a white dwarf as a parent star, an exoplanet might be larger than its sun. The planet could therefore block a large portion (or even all) of the star’s light when passing in front of it; even in the absence of a transit, there might be a significant signal from reflected starlight when the planet passes behind the star. Using backyard-scale telescopes (11- to 24-inch) and CCD imagers, Bruce Gary and his team are achieving astounding levels of precision — 2 to 4 millimagnitude, or differences in brightness of a few thousandths —.in their search for variations in starlight that would indicate a planet’s presence. Over two years they detected periodic dips of about one-hundredth magnitude every 2.69 hours from the white dwarf WD 2359-434. This might be a long-lived starspot, or it might be an exoplanet.

Jovian satellites: Using small telescopes and video cameras similar to those many amateurs use to monitor asteroid occultations, a network of amateurs is observing occultations and eclipses of Jupiter’s moons. The idea is that careful photometry of these events can reveal the moons’ tenuous atmospheres and gas and dust exhalations. Scott Degenhardt and Wayne Green presented back-to-back papers on these so-called “Jupiter Extinction Events,” a topic that has come a long way since Degenhardt described his first tentative (and controversial) observations several years ago.

Watching the asteroid turn: Kevin Ryan presented the results of an international collaboration of small-telescope researchers that appear to resolve a nagging uncertainty about the asteroid 1110 Jaroslawa. The previously reported light curve for this object looked nothing like what is expected from a rotating, elongated object; in fact it is very hard to imagine what sort of object shape could give rise to such a pattern. Taking advantage of amateurs’ willingness to devote a long series of all-night sessions to monitoring a single object, Ryan’s project mapped nearly a complete light curve for the asteroid and found that it displays the more “normal” shape expected from a football-shaped asteroid rotating end-over-end. Happily, when the previous data were analyzed using the improved rotation period found by Ryan, they fell nicely into line with his result.

Lights no danger for astronomers: Eric Craine presented a careful study of a recent roadway lighting project in Sedona, Arizona, which had an unexpected (but wonderful) result. Most amateur astronomers are rightly concerned about the proliferation of nighttime lighting and its potential consequences for astronomy, wildlife migration, and human health. So when the Arizona Department of Transportation proposed to significantly increase the lighting along the main highway through Sedona, quite a few interested groups opposed it. However, there were virtually no quantitative data on the baseline levels of sky glow. Craine conducted both ground and airborne surveys of the sky brightness, both before and after the roadway lighting upgrade was completed. His report contained two significant messages:

1. There was no statistically significant change in sky brightness after the project was completed — even though it dramatically improved the lighting on the roadway and sidewalks. The Arizona DOT did an excellent job in designing and implementing this project!

2. The community is poorly served if it reacts with kneejerk opposition to a lighting project, instead of depending on relevant quantitative data. The Sedona project appears to be a fine example of how lighting can protect both public safety and dark skies.

Videos of these presentations and all of the other technical papers from the 2013 SAS Symposium will be available on the SAS website within a few weeks. You can also read highlights from the 2012 meeting.


SAS board member Robert Buchheim is the author of The Sky Is Your Laboratory, a manual for research-oriented amateur astronomers, and received the Western Amateur Astronomers’ G. Bruce Blair award in 2010 for his encouragement of amateur science.

Proxima Centauri's pass by two distant stars might reveal details about itself and whether it hosts any planets.

Astronomers love spying on neighbors. And in the next three years, they may have two chances to take a rare peek at the Sun’s closest stellar neighbor, Proxima Centauri. This morning at the summer meeting of the American Astronomical Society, Kailash Sahu (Space Telescope Science Institute) reported that this small, cool M-type star may be about to reveal both its own details and whether it hosts any planets.

Proxima Centauri is only 4.2 light-years away, but it’s pretty tight-lipped about itself. It’s too distant a relation to Alpha Centauri A and B, with which it forms a triple system, for astronomers to precisely calculate its mass from the stars’ swings around one another. Furthermore, multiple attempts to detect a planet around Proxima have produced only null results. Those null results rule out planets (1) larger than Neptune within 1 Earth-Sun distance of the star, (2) Jupiters with orbital periods from 1 to 1,000 days long, and (3) planets crossing directly in front of the star from our vantage point, Sahu said. That still leaves wiggle room.

But taciturn Proxima didn’t count on backlighting. In October 2014, it will start its pass within two arcseconds of a distant star; in February 2016 it will come 0.5 arcsecond to another one. Both stars are about magnitude 19 to 20, much fainter than Proxima’s 11th magnitude. But when Proxima passes by, the light from those stars will bend around Proxima to reach us, creating a tiny deflection in their apparent positions. How strong this lensing effect is will depend on Proxima’s mass.

The distant starlight might also have to contend with any planets around Proxima. If a planet orbits within 4 Earth-Sun distances, that planet could also lens the distant starlight, creating a spike in the background star’s brightness that could last for about three days, Sahu said. How much the light spikes depends on how far the planet is from Proxima itself. This microlensing technique has produced exoplanet results before, notably with the MicroFUN project.

Sahu and his colleagues already plan to use the Hubble Space Telescope to observe the 2014 event, but they’re hoping for help — including from well-equipped amateurs. Observers would need to have a good view of the southern sky and be able to observe down to 20th magnitude. He’s planning to set up a website with details on the star’s path and whatnot as the 2014 event approaches.

From international travel to interplanetary probes, the U.S. budget cuts are having impacts on both ground- and space-based astronomy.

In early May, a brief announcement appeared on the website of NASA’s Kepler mission. It read, in full: “The Kepler Science Conference originally scheduled for fall 2013 has been cancelled.” Left unsaid was the reason why, which could have been even briefer: “Due to sequestration.”

Astronomers took to Twitter to voice their dismay as word spread. “Arguably one of NASA’s most successful recent missions finding Earth-sized planets, and scientists can’t get together to discuss,” tweeted Caltech’s Peter Plavchan. The conference would have brought hundreds of astronomers to NASA’s Ames Research Center in California to present and discuss the satellite’s most recent results. Instead, it became the latest sign of how U.S. astronomy and space science will suffer from the federal sequestration cuts.

The abrupt, mandatory reductions fall against the backdrop of an already turbulent fiscal scenario, and unless it is lifted, it will turn the budget screws even tighter on the two largest U.S. government funding agencies for astronomy: the National Science Foundation (NSF) and NASA. If left unchecked, scientists and administrators warn of dire consequences for the nation’s scientific and economic competitiveness.

NSF Researchers Will Feel Cuts

NSF funding forms the public backbone of U.S. ground-based astronomy, underwriting national facilities open to all U.S. astronomers and awarding about $80 million in research grants in fiscal year 2012. Sequestration cut NSF's FY 2013 overall budget by approximately 5%, and although this was partially offset by a last-minute increase in the FY 2013 budget passed by Congress in late March, the net result is still a 2.1% cut relative to FY 2012.

It’s not yet known how exactly it will fall across its science divisions, but James Ulvestad, director of the agency’s astronomy division says, “The most immediate impact will be on our small- and mid-scale research grants programs.” All existing grants will be honored in full, but Ulvestad estimates that the number of new grants awarded, already heavily oversubscribed, will fall by about 15 to 30% in FY 2013. Not only will established researchers suffer, but also “fewer graduate students will get support, and fewer postdoctoral fellows will get support,” says Joel Parriott, director of public policy for the American Astronomical Society (AAS).

If sequestration were to remain in effect indefinitely, Ulvestad anticipates a laundry list of dangerous effects. The lack of research grants might cede the most exciting discoveries on its own facilities to researchers elsewhere. A shortfall of infrastructure funding might threaten the construction of the large facilities recommended by U.S. astronomers’ 2010, once-a-decade roadmap, including the Large Synoptic Survey Telescope. And the NSF cuts are only part of the broader federal science budget, “reducing a position of world leadership and imperiling the training of a new generation of STEM professionals.”

Sequester Curtails NASA’s Outreach, Conferences

One of NASA’s first responses to its mandatory 5% cut was the March suspension of education and public-outreach activities. This prompted an outcry from the educators and writers employed by NASA missions to relate their findings to the taxpaying public. The situation was somewhat eased by the announcement of wide-ranging exemptions, though many say it only muddled the issue further, making it difficult to estimate the reduction’s true impact. (Read a sampling of the responses here.)

Perfectly evident, however, are the effects of the restrictions on conference-related travel that followed, eliminating international travel and preventing more than 50 NASA personnel from attending any single conference. Next week’s meeting of the American Astronomical Society is just one conference that has shrunk in the absence of NASA scientists and exhibitors. The effects multiply: Attending scientists who would normally be at their peers’ talks will instead have to multitask by staffing exhibits, according to Debbie Kovalsky, AAS’s exhibits coordinator. And commercial vendors whose clients will no longer be there have decided to skip it or downsize their presence as well.

NASA managers have further announced a string of cancelled conferences aside from December’s Kepler Science Conference, including a data calibration meeting for Hubble results and the annual Sagan Exoplanet Summer Workshop.

“Conferences are where part of the scientific process happens,” says Peter Plavchan, who has authored four papers using Kepler data. “Canceling this conference will slow down the process of discovery, and taxpayers won’t get the most new discoveries for their dollar as a result.”

“NASA spends $98M a year to operate Hubble,” noted the scientists on the astrophysics subcommittee of NASA’s Advisory Council in an April letter. “Canceling a Hubble science conference saves only $50K, but diminishes the science impact of Hubble. This is simply not cost effective.”

Planetary Science Fights for Funds

Perhaps the most politically embroiled impact of sequestration on space science has been the budget figure for NASA’s solar-system division, responsible for successes like the Cassini probe at Saturn and the recent run of rovers on Mars. Planetary science has weathered severe cuts in recent years caused in part by cost overruns of the James Webb Space Telescope (JWST), prompting what Nature News described as “internecine warfare” between supporters of astrophysics and planetary missions.

The Obama administration’s FY 2013 budget request slashed planetary funding by more than 20%, to less than $1.2 billion. But a bipartisan group of supporters in Congress countered by inserting an additional $222 million into its FY 2013 appropriations bill, which President Obama signed in March.

However, sequestration offered NASA an opportunity to reshape its appropriations internally. Instead of spreading the cuts across all divisions equally, NASA’s operating plan for the rest of FY 2013 singles out planetary science for a 15% cut, according to a copy obtained by Mark Sykes of the Planetary Science Institute. The result wipes out all but $3.7 million of the additional $222 million allocated by Congress.

In other words, says Sykes, the Obama administration and NASA used the sequestration cuts as a means to evade Congressional intent. “To come in and sweep away more than 98% of the funds added by Congress and signed into law was very surprising,” Sykes told me. “I thought it was disdainful.” Casey Dreier of the Planetary Society did little to hide his shock in a blog post titled, “NASA Robs Planetary Science.”

NASA’s plan did retain good news for some planetary scientists — $66 million in funds for studies of a potential flagship mission to Jupiter’s icy moon Europa, whose subsurface ocean is one of the most enticing places to search for extraterrestrial life. However, instead of using the money that Congress had allocated for it, NASA and the administration effectively took it out of other programs, dropping them below the President’s proposed FY 2013 levels, including competitive research grants and smaller missions under the Discovery and New Frontiers programs. “Rob Peter to pay Paul, is what it is,” Sykes lamented. While he’s not opposed to a Europa mission, “additional studies should be funded by additional monies — not at the expense of research, Discovery, or New Frontiers.”

This challenging fiscal environment shows no sign of abating: in the President’s FY 2014 request, planetary science again came up $200 million short of the FY 2013 level allocated by Congress in March. In what educators say is a further attack on science education, it also proposes removing all NASA-related education and outreach from the space agency’s purview and reconstituting it under the Department of Education and the Smithsonian. The goal is to improve efficiency, but many say it would destroy the existing networks between educators and scientists and even backfire. “This will likely necessitate new layers of personnel to interface between NASA scientists and educational professionals,” noted NASA’s astrophysics advisory subcommittee. Altogether, these developments paint a bleak picture for many. “I’m not sure what the administration’s plans for the future are,” says Sykes. “But if it involves decimating our capability [as a nation], I think they’re taking the right steps.”

NSF Divestment Continues

One thing the sequester will not affect, says James Ulvestad, is NSF’s ongoing plan to divest its interests in several ground-based facilities, including the Green Bank Telescope, the Very Long Baseline Array, and three optical telescopes at Kitt Peak National Observatory (KPNO) in Arizona. (This is a result of a 2012 portfolio review assessing NSF Astronomy’s long-term financial picture.) “That timescale was set up to provide a reasonable (but not excessive) period of time to enable new partnerships and new operations models to develop,” says Ulvestad.

At Kitt Peak, where NSF acts as the observatory’s landlord, the Department of Energy and the University of California-Berkeley are currently interested in such a partnership to use the Mayall 4-meter telescope to conduct an all-sky dark-energy survey. A private grant will fund the construction of the instrument, but ultimately, the decision to fund the project remains with DOE. “Optimism for the future is considerably higher today than it was a year ago,” says KPNO’s director, Timothy Beers. “But if you ask me today, ‘Will Kitt Peak be a living, viable observatory doing astronomical research 10 years from now?’, I will know better in a year or two … I can’t say what the path toward that is.”

High-definition images of the Moon and Mars show that their surfaces take hundreds of hits each year from space rocks.

Last week I wrote about the brightest lunar impact ever captured by a research team at NASA's Marshall Space Flight Center. The March 17th blast momentarily reached 4th magnitude — it might have been observable to a keen-eyed observer just looking at the Moon.

Based on that bright flash, the team estimates that the wayward space rock was perhaps the size of a beach ball. In this case, the team assumes the impactor was one member of a salvo, traveling through space with others seen streaking through Earth's atmosphere at roughly the same time. Given that, they deduced a common orbit and an impact velocity of 57,000 miles per hour (25.6 km per second).

But converting the brightness of an impact flash to mass and velocity is something of a black art, one often applied to bright fireballs in Earth's atmosphere (February's megameteor over Russia, for example). Many of the hundreds of other lunar flashes seen throughout the NASA team's eight years of observations occurred during meteor showers such as the Geminids, so their impact velocity was known. Even so, the impactors' sizes are really educated guesses.

Fortunately, the advent of supercameras on orbiting spacecraft — LROC on the Lunar Reconnaissance Orbiter and HiRISE on the Mars Reconnaissance Orbiter — has made it possible to identify hundreds of fresh but very small impact craterlets on both the Moon and Mars. These offer a much tighter constraint on the kinetic energy of each strike and, from that, better estimates of the impactors' sizes.

LROC has been recording details on the Moon down to 8 inches (20 cm) for nearly four years, and it's starting to see lots of lunar real estate with nearly identical illumination. Shane Thompson and Mark Robinson (Arizona State University) have combed through the camera's thousands of images and turned up 69 "temporal anomalies" that are definite or likely cratering events. About 20% of these show distinct craters, the largest 24 feet (7.3 m) across. A summary of their work to date reveals two striking results (no pun intended).

First, most of the fresh markings are darker, not lighter, than the background surface. We've all been taught that fresh lunar craters kick up a splash of light-toned dust that gradually darkens with exposure to radiation. But apparently, at least for the small fry, that's not usually the case. Thompson notes that these murky smudges aren't in known lava deposits covered by a layer of disguising dust ("cryptomare"), so their origin is a mystery. (Curiously, both GRAIL spacecraft churned up dark ejecta when they struck the Moon last December.)

The second eye-opener is that Thompson and Robinson found so many cratering candidates in just 31 pairs of images. Based on those statistics, they estimate that the Moon gets peppered with 180,000 impacts per year that could be picked out by LROC's high-resolution camera. This corresponds to about one hit annually in an area the size of the District of Columbia — the kind of frequency that would pose a small but very real risk of damage to future lunar colonies.

In the case of Mars, the crater-hunting challenge is a little easier because the planet's atmosphere, though quite thin, keeps the ejecta suspended longer and thus helps to expand the surface area disturbed around each strike. The first reports of newfound craters came from the Mars Orbiter Camera, which spotted 20 impacts — the largest 500 feet (150 m) across — over a 7-year stretch.

HiRISE researchers recently detailed the 248 fresh impact craters they've spotted on the Martian surface over the past decade. Based on those finds, Ingrid Daubar (University of Arizona) and others estimate that each year the Red Planet gets more than 200 new craters at least 12.8 feet (3.9 m) across. More than half of the impacts in this size range form clusters. These are created by strikes by asteroid or comet fragments no more than 3 to 6 feet (1 to 2 m) across.

Put another way, each year Mars gets one crater of that size or larger for every 230,000 square miles (600,000 km²) of its surface. That's actually well below the rate expected by extrapolating downward to such small sizes from counting larger craters. As Daubar and others note in the July issue of Icarus, they might be overlooking a few new pits in dusty areas. But more likely, they conclude, "order-of-magnitude uncertainties persist" in our ability to model the planet's long-term cratering rate, especially at small diameters.