The Hoba meteorite in Namibia, Africa, the largest known
meteorite found; approximately the size of 2008 TC3 before
it burned up in our atmosphere.News Flash! Asteroid 2008 TC3, on a collision trajectory with Earth, made a meteoric atmospheric entry into the skies above Sudan, Central Africa Tuesday morning, October 7^th (local time-about 7:46 PM PDT). Entering the atmosphere at a speed of 12.8 kilometers per second, it exploded with the force of a low-level nuclear bomb…

Wait a moment… an asteroid you say? Hitting the Earth? Isn’t that supposed to spell some kind of disaster, such as Dino-slaughter? Isn’t that something we send people like Bruce Willis and Clint Eastwood to deal with before it becomes a problem down here on Earth?

Okay, so Asteroid 2008 TC3 wasn’t an Earth-killer, but rather a crowd-thriller. It wasn’t miles across-not even tens of meters across. It was, perhaps, a few meters in size, similar in volume to mid-size car. In fact, it didn’t even hit the Earth’s surface, but vaporized in the atmosphere.

Sounds a bit anticlimactic-and that’s not the half of it. It’s not even a rare event! Objects of this size are believed (and sometimes observed) to enter Earth’s atmosphere a few times each year. So what’s the blog deal?

The blog deal is this: this is the first time that an object this size has been detected approaching the Earth a significant period of time before actually impacting-in this case, about a day. 2008 TC3 was detected by the Mount Lemmon telescope in Arizona on Monday. The detection was reported to the Minor Planet Center, which collects such observations from observatories large and small (including Chabot Space & Science Center) in order to track and predict possible Earth impactors. In turn, the MPC alerted NASA of the impending impact.

Observers on the ground reported the fireball lit up the skies with the intensity of the Full Moon. A nearby airliner (not in danger, as the fireball exploded tens of kilometers above the ground, well above the airliner’s flight path) reported seeing a bright flash.

In a sense, this event was kind of a dress rehearsal for the international system of predicting, and possibly defending against, impacts on Earth by much larger asteroids and comets. We already know of thousands of Near Earth Objects (NEOs-asteroids and comets that cross Earth’s orbit and are large enough to cause a catastrophe should they strike the Earth). It is also expected that there are many thousands more that we haven’t yet detected, being small enough to “fly under the radar” of our NEO detecting network.

Early detection and sustained tracking of NEOs is key to the protection plan against impact disaster. If we can accurately predict an impact far enough in advance, we could potentially send a spacecraft to it and gently “nudge” it off course and deflect the eventual impact.

So ends the existence of another chunk of rock that had, up to that point, been serenely orbiting the Sun for billions of years…

Artist concept of lightning on Venus. Credit: NASAVenus has reentered our sky in its part-time job as the Evening Star, appearing as a uniquely brilliant white beacon over the western horizon after sunset.

With all the attention that the exploration of certain other planets has received lately, I feel that Venus exploration has fallen off our radar a bit, and that it is high time for an update.

There is no lack of exploration of Venus today: NASA’s MESSENGER spacecraft, bound for Mercury, flew by Venus twice (2006, 2007), making observations on the fly; Japan is currently planning to send a climate orbiter mission (“Planet C”) there in 2010; and the European BepiColombo will perform a couple of Venus flybys of its own, in 2013, on its way to Mercury.

Most notably, the European Venus Express orbiter is in the middle of a two-year mission of exploration, and has revealed new and fascinating things about Venus–a planet whose cloud-shrouded surface kept us mostly ignorant about it until recent decades. (Before the 1960’s it was even speculated that Venus might be a steamy swamp or rain forest world!)

Here’s a quick recap of some of the highlights of Venus Express’s findings:

“Hurricanes” at the poles: Venus Express’s VIRTIS instrument, which is able to probe several different layers of the atmosphere, has put together a detailed picture of wind behavior at different latitudes and different altitudes. What was discovered from these observations is that Venus has giant, hurricane-like vortexes capping its poles. Winds within these systems all flow in generally the same direction, as you’d expect with hurricanes, circling mostly windless “eyes” at their centers at the poles.

Lighting: Evidence of lightning on Venus was detected by earlier orbiter and lander missions, and Venus Express has confirmed it–maybe more lightning activity than on Earth. What makes Venus’s lightning unique among the planets with lightning (Earth, Jupiter, and Saturn, as far as we know) is that it’s the only case where lightning is formed by something other than clouds of water droplets–in Venus’s case, sulfuric acid droplets do the trick. Lightning can be an important factor in that it breaks up atmospheric molecules and allows them to recombine in different forms.

Active volcano search: It has long been suggested that there may be active volcanoes on Venus today, though no direct evidence (like images of erupting volcanoes, for example) have yet been obtained. Venus Express has measured large variations over time in the concentrations of sulfur dioxide in Venus’s atmosphere–a compound that on Earth comes from volcanic eruptions.

There’s a lot more to say about Venus, as it is a world as varied and fascinating as the Earth (minus the life forms, as far as we know). Though it may not be the hottest vacation spot in the solar system, with its pressure cooker of a toxic, acid-laced atmosphere, it is one of those great mysteries that we actually get to watch unfold before us as exploration of it moves forward.

Asteroid 35107, captured on Chabot Space
& Science Center’s telescope.

Photo By Conrad Jung and Gerald McKeegan

You must be very quiet; we are hunting…asteroids!

On July 14th, 2008, an almost Hollywood-like drama took place in space nearby: a “double,” or binary, asteroid whizzed past Earth, grazing by at a distance of only 1.4 million miles. One of the rocks is over 200 meters across, the other a whopping 600 meters-about half the size of Half Dome in Yosemite!

1.4 million miles may sound like a large distance, but by the standard of big rocks flying by the Earth, that’s breathtakingly close. Discovered only last January, this pair of asteroids went from being completely unknown to blasting by Earth’s doorstep in only months. Had they actually hit the Earth, they would have caused major devastation at and near the impact site, with very little warning.

Fortunately, there are programs to search for and track these flying mountains-also called “Near Earth Objects” (NEOs)-and I’m very pleased to announce that Chabot Space & Science Center (specifically our 36-inch reflecting telescope, “Nellie”) has very recently become an official contributor to the NEO search program of the International Astronomical Union’s Minor Planet Center (MPC)! Nellie is designated by the MPC as Observatory G58.

In this MPC program, observatories around the world contribute by searching for and tracking NEOs: asteroids, and comets, whose orbits can carry them close to Earth and which are large enough to cause catastrophic damage should they hit us.

In order to take part in the NEO program, Chabot observers Conrad Jung (on the Chabot staff) and Gerald McKeegan (of the Eastbay Astronomical Society) conducted a four-month program to develop and hone the necessary skills and data processing techniques, as well as to configure telescope equipment, to meet MPC qualifications.

To that end, they observed a set of known asteroids-some NEO’s and some “Main Belt” asteroids. (One of these Main Belt asteroids, “Carter 10683,” was named for former Chabot board member and president of the Eastbay Astronomical Society, Carter Roberts, who, sadly, passed away earlier this year.)

Chabot’s asteroid hunters will begin their tenure of official asteroid observation by verifying the orbits of recently discovered NEOs and reporting the additional observations to the MPC, where it will be used to refine our knowledge of the NEOs’ orbits. The next step in the program will ultimately be to hunt for currently undiscovered asteroids.

The process for finding, tracking, and reporting NEO observations goes something like this. With a digital (CCD) camera attached to the telescope, a section of the sky is imaged three or four times in a half-hour period. The images are processed and compared, and any star-like dots that are found to move between one image and the next become suspect asteroids. (The word “asteroid,” by the way, literally means “star-like”-so named because through most telescopes asteroids are too far away and too small to appear as anything more than points of light.)

The coordinates of any moving dots are calculated for all of the images they are in, and this information is sent to the MPC to be added to the data from other NEO hunting observatories. From the combined observations of all the observatories, a precision database of the orbits of near-Earth rocks is maintained, and with it NEOs that may pose a threat to the Earth may be identified.

Hunting NEOs may be like searching for needles in a really big haystack-but in jobs like this, the more eyes on the problem the better. Nellie is now one more eye on lookout duty…

Click here for a closer view of the asteroid shown above.

Depiction of a major alignment of
the five visible planets in 1059 BCE.

Photo By Ben Burress

There are some pretty good “lineups” coming soon to skies above you.

First of all, “lineups,” or alignments, go on in the heavens all the time, though most often they are alignments of objects too faint to easily notice, if at all. With that said, this summer holds some significant alignments of some of the brightest objects in the sky.

First on my hit list is the upcoming Saturn-Mars “near-miss”. Though these two planets are not coming physically close to each other (the closest actual distance they come to each other is about 750 million miles), they will align so closely along the same line of sight that on July 11^th they will appear only ¾ of a degree apart-that’s not much greater than the width of a Full Moon. The best time to see this pairing is after sunset on the evenings of July 10, 11, and 12, over the western horizon.

The next big ticket alignment is on August 1^st, when the Moon and the Sun occupy the same spot in the sky-the event we call a Total Solar Eclipse. As it happens, we won’t be able to see this eclipse directly from the United States, as it will only be visible in Asia. However, NASA will be broadcasting live coverage of the eclipse from Northern China. We’ll be showing NASA’s broadcast in our planetarium at Chabot Space and Science Center, in case you’d care to come up and enjoy the spectacle. Don’t let the fact that the live event goes on around 4:00 AM keep you away…it’s worth getting up for!

A bit further out on the calendar is the September alignment of three planets: Venus, Mars, and Mercury. In the dusky twilight of mid-September evenings the three will be gathering. The closest grouping of the trio is on September 11^th, when they will be within about three degrees of each other-close enough that you can just about cover all three with your thumb. Mercury and Mars won’t be very bright in the twilight-but Venus, bright enough to spot easily, can help guide your eye to the other two. Using a pair of binoculars will help a lot-but make sure you don’t point them that way until after the Sun sets….

In ancient times (and in some cases not so ancient times), different cultures around the world have viewed alignments like these in different ways. Eclipses-both solar and lunar-were regarded by many cultures as bad omens, or bad occurrences (such as the Sun being devoured by a celestial animal-dragon, dog or other-in the case of a solar eclipse).

Planetary alignments were also given special consideration, sometimes being regarded as auspicious (for good or bad-usually the latter). One major alignment of the five visible planets (February 26, 1953 BCE) was believed to have “mandated” the creation of the Hsia Dynasty in China-the first great Chinese Dynasty. (Then, four centuries later, Mars, Mercury, Jupiter and Saturn apparently conspired to bring down that same dynasty-at least, their alignment on December 20, 1576 BCE was interpreted as an indicator of the dynasty’s corruption, and it was overthrown by a revolt of believers…).

However you regard the lining up of celestial bodies (astronomically, astrologically, or aesthetically), these alignments are pleasing to watch, and times to reflect upon the constant and cyclic movement among the heavens. Enjoy….

A patch of what might be ice, exposed by Phoenix’s
landing rockets.So, did it land on ice? Huh? Did it?

Two blogs ago I wrote about the then upcoming landing of the Phoenix spacecraft on Mars, near the Northern polar ice cap (Probing the Martian Pole). The entire point of landing on Mars’ extreme northern plains was to find and examine ice-ice we know is up there in great abundance, as detected by orbiting spacecraft (Mars Odyssey 2001).

There, frozen under the surface dust layers, is a vast deposit of ice-”enough to fill Lake Michigan twice.” So Phoenix was sent to actually land there and scrape up surface samples of the soil, and hopefully ice. The question was, would the layer of dust covering the ice be thin enough for Phoenix to reach the ice with its robotic arm and shovel?

The landing occurred on May 25th-a successful landing. NASA broadcast the drama live on NASA TV, which we shared with several hundred Chabot visitors via planetarium, theater, and closed-circuit TV. There were no actual images coming from Phoenix during the landing-after all, it was cooped up in its protective shell for much of the descent-but the excitement of the real-time drama and the nervous faces of NASA/JPL were enough to enthrall our audience. Pictures wouldn’t come form Phoenix until later that night at the earliest.

But the pictures did come in over the days following. At first they looked much like images from other Mars landers (Viking, Pathfinder, Spirit, Opportunity), only flatter. Rusty red soil, low flat horizon, a scattering of pebbles and rocks. The landscape itself appeared less interesting to me than other landing sites-but if you measure Phoenix’s success by the beauty of the scenery, you’re missing the point.

Phoenix is pretty much all about the ice, and what chemicals are frozen and preserved in it. The questions asked by the Phoenix mission are: did life ever arise on Mars, is the current climate on Mars suitable to support life, and what is Mars’ geological makeup? If the vast ice deposits of the flat northern hemisphere lowlands are the frozen leftovers of what was once a liquid sea, then are there chemical clues of past conditions-even past life-locked up and preserved there?

So, do we have answers to these questions yet? Is there ice under Phoenix within reach of its scooper? At the time of my writing this the answer is: maybe. During the first week of testing Phoenix’s systems to get it ready for full-on prospecting, a picture of the ground underneath the lander was taken using the camera attached to the robotic arm. This picture revealed a patch of solid substance that seems to have been exposed by the blast of Phoenix’s landing rockets. It looks like it could be ice, but until a sample is analyzed we won’t know for sure (because, it could be solid rock, too).

The first sample scoop of soil dug up by Phoenix’s shovel was placed in a bucket on board the lander and examined by camera, before being carefully dumped into a designated sample waste location (Mars’ first land fill). The picture revealed some white substance in the reddish soil-which could be ice, or possible salt.…

Stay tuned in the coming days and weeks for hot news from the ice as Phoenix conducts its investigations in earnest.