The first spacecraft to orbit an asteroid has been renamed to honor geologist Eugene M. Shoemaker. The Near Earth Asteroid Rendezvous (NEAR) spacecraft, which has been circling the asteroid 433 Eros since February 14th, will now be known as NEAR Shoemaker. The announcement was made on March 14th at the Lunar and Planetary Science Conference in Houston, Texas, by Carl B. Pilcher, Director of Solar System Exploration at NASA Headquarters. "Gene Shoemaker was an inspirational, charismatic pioneer in the field of interplanetary science," Pilcher explained. "It is a fitting tribute that we place his name on the spacecraft whose mission will expand on all he taught us about asteroids, comets, and the origins of our solar system."

NEAR Shoemaker currently orbits Eros about 200 kilometers from its center, taking 9 days to complete one revolution (Eros itself rotates every 5.27 hours). The orbit will be shrunk to 100-km radius on April 1st, and soon thereafter NEAR should be circling at just 50 km -- close enough to use its magnetometer and X-ray/gamma-ray spectrometers.

At the conference, Donald K. Yeomans (Jet Propulsion Laboratory) reported that Eros's mass has been determined to be 6.7 x 10^18 grams. This yields a bulk density of 2.7 grams per cubic centimeter. This value could change somewhat once researchers refine the shape of the 33-by-13-km body and accurately determine the asteroid's volume.

CORVALLIS, Ore. -- Researchers say in a new report that if a huge asteroid were to hit the Earth, the catastrophic destruction it causes, and even the "impact winter" that follows, might only be a prelude to a different, but very deadly phase that starts later on. They're calling it, "ultraviolet spring."

In an analysis of the secondary ecological repercussions of a major asteroid impact, scientists from Oregon State University and the British Antarctic Survey have outlined some of the residual effects of ozone depletion, acid rain and increased levels of harmful ultraviolet radiation. The results were just published in the journal Ecology Letters.

The findings are frightening. As a number of popular movies have illustrated in recent years, a big asteroid or comet impact would in fact produce enormous devastation, huge tidal waves, and a global dust cloud that would block the sun and choke the planet in icy, winter-like conditions for months. Many experts believe such conditions existed on Earth following an impact around the Cretaceous-Tertiary, or K-T boundary, when there was a massive extinction of many animals, including the dinosaurs.

That's pretty bad. But according to Andrew Blaustein, a professor of zoology at Oregon State University, there's more to the story.

"Scientists have pretty well documented the immediate destruction of an asteroid impact and even the impact winter which its dust cloud would create," Blaustein said. "But our study suggests that's just the beginning of the ecological disaster, not the end of it."

Blaustein and colleague Charles Cockell examined an asteroid impact of a magnitude similar to the one that occurred around the K-T boundary, which is believed to have hit off the Yucatan Peninsula with a force of almost one trillion megatons.

The immediate results would be catastrophic destruction and an impact winter, with widespread death of plants and the large terrestrial animals -- including humans -- that most directly depend on those plants for food. That's the beginning of an ugly scenario, the researchers say.

As a result of the impact, the atmosphere would become loaded with nitric oxide, causing massive amounts of acid rain. As they become acidified, the lakes and rivers would have reduced amounts of dissolved organic carbons, which would allow much greater penetration of ultraviolet light.

At first, of course, the ultraviolet rays would be blocked by the dust cloud, which sets the stage for a greater disaster later on. Many animals depend on some exposure to ultraviolet light to keep operational their biological protective mechanisms against it -- without any such light, those protective mechanisms would be eroded or lost.

During the extended winter, animals across the biological spectrum would become weaker, starved and more vulnerable. Many would die. Then comes ultraviolet spring, shining down on surviving plants and animals that have lost their resistance to ultraviolet radiation and penetrating more deeply, with greater intensity, into shallow waters than it ever has before.

"By our calculations, the dust cloud would shield the Earth from ultraviolet light for an extended period, with it taking about 390 days after impact before enough dust settled that there would be an ultraviolet level equal to before the impact. After that, the ozone depletion would cause levels of ultraviolet radiation to at least double, about 600 days after impact."

According to their study, these factors would lead to ultraviolet-related DNA damage about 1,000 times higher than normal, and general ultraviolet damage to plants about 500 times higher than normal. Ultraviolet radiation can cause mutations, cancer, and cataracts. It can kill plants or slow their growth, suppressing the photosynthesis which forms the base of the world's food chain.

Smaller asteroid impacts, which have happened far more frequently in Earth's history, theoretically might cause similar or even worse problems with ultraviolet exposure, the researchers say. The ozone depletion would be less, but there would also be less of a protective dust cloud.

"Part of what we're trying to stress here is that with an asteroid collision, there will be many synergistic effects on the environment that go far beyond the initial impact," said Cockell, a researcher with the British Antarctic Survey who did some of this analysis while formerly working with NASA. "Effects such as acid rain, fires, the dust clouds, cold temperatures, ozone depletion and ultraviolet radiation could all build upon each other."

During the K-T event, the scientists said, many of the animals may actually have been spared most of the ultraviolet spring they envision. That impact, oddly enough, hit a portion of the Earth's crust that was rich in anhydrite rocks. This produced a 12-year sulfate haze that blocked much of the ultraviolet radiation. But it was a lucky shot -- that type of rock covers less than 1 percent of the Earth's surface.

So when the next "big one" comes, the scientists said, the ecological repercussions may be more savage than any of those known in Earth's long history. The collision will be devastating, the "impact winter" deadly.

But it will be the ultraviolet spring that helps finish off the survivors.

Cruising toward its arrival at Jupiter next December, the Cassini spacecraft passed in the vicinity of minor planet 2685 Masursky on January 23rd and took a series of snapshots from 1.6 million kilometers away. According to Carolyn Porco, who heads Cassini's imaging team, the little asteroid has a diameter of about 15 to 20 km. Although its disk was not resolved, Masursky's reflectivity suggests that it may not be an S-type asteroid, as had been assumed based on its orbital association with the Eunomia family of S-type asteroids. This object was named for renowned planetary geologist Harold Masursky (1923-90). "It may be only a dot," says Porco, "but it's a very special dot to us!"

Wanted: A Few Good Solar Flares - A 15-second engine burn on March 3 will move NEAR into a tighter orbit around Eros. With a little help from the Sun, the satellite could get its first readings of the Eros's composition.

March 3, 2000 -- A 15-second engine burn at 1 p.m. EST on March 3 will nudge NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft into a 200-kilometer (124-mile) orbit around Eros, giving the probe its best scientific look at the asteroid so far.

"We expect to resolve a lot of the features that we've only seen glimpses of," says Louise Prockter, a member of NEAR's imaging team.

With a little help from the Sun, the satellite could also get its first readings of the asteroid's elements. The X-Ray Spectrometer detects fluorescence from substances that react to cosmic x-rays. X-rays from solar flares that illuminate the asteroid will cause surface elements such as magnesium, aluminum, and silicon to glow with their own characteristic X-ray signature that the spectrometer can record and decipher.

"A lot depends on solar activity," says Ralph McNutt, X-Ray/Gamma Ray Spectrometer instrument scientist. "If there is a strong solar X-ray event, the instrument will get a good measurement."

McNutt's wish is likely to come true. The face of the Sun is currently peppered with active sunspot groups. Three of them have complex magnetic field structures that make significant eruptions almost certain. In the past 24 hours alone the NOAA GOES-8 satellite has recorded four intense X-ray emitting flares. As NEAR descends toward Eros, the space weather environment looks just right for some good X-ray fluorescence measurements.

The craft's radio science equipment will also take advantage of the closer orbit to get a better reading of the asteroid's gravity field. This will help scientists piece together the internal structure of the asteroid and allow ground controllers to manage NEAR's tricky orbit around the low-mass space rock.

Pinging all Space Rocks

On February 29, the NEAR Laser Rangefinder (NLR) detected the first laser returns from Eros at a range of 290 km. NLR was designed to operate at 50 km range, and its successful detection of Eros at 290 km bodes well for the future, say mission scientists.

Left: The first laser rangefinder observations were obtained during the turn-on of the instrument while the NEAR spacecraft orbited Eros on February 28-29, 2000. The returns from this calibration pass bounced off a short segment of the surface, close to the edge of a giant gouge.

"The laser rangefinder data will give us a three-dimensional view of the asteroid surface, nicely complementing the information from images," says Andy Cheng, the NEAR Project Scientist at Johns Hopkins University. "This is because imagers record the distribution of brightness as a function of angles perpendicular to the line-of-sight, whereas the laser rangefinder measures distance to the surface along the line-of-sight. The combination of the two data sets will be powerful, as we hope it will enable us to probe into shadowed regions (because the laser does not depend on solar illumination), and to distinguish between effects of albedo [reflectivity] variations and effects of height variations."

Moving 3 miles an hour relative to Eros, NEAR will circle the rotating space rock three full times during the upcoming 200 km (124 mile) orbit. NEAR operates at this range until April 1, when another short engine burn will gradually move it into a 100-kilometer (60-mile) orbit. The asteroid and spacecraft are about 245 million kilometers (152 million miles) from Earth.

The NEAR team will analyze and present its findings from the orbit over the next several months, including a potential first look at the data during a March 13 press briefing at the Lunar and Planetary Science Conference in Houston.