The bad thing about science is that it lets us know just how precarious our position is.  Our ancestors were blissfully ignorant, thinking they were living in a safe and unchanging world.  Now we know that this was only a misconception caused by lack of knowledge.  As we get smarter, we realize just how dangerous this universe is, and how quickly and completely our little corner of it could change.  All the bodies of the solar system, including Earth, are pockmarked with the prints of past impacts, and more of them are being discovered all the time.

There are many examples.  In 2004, for instance, a systems analyst in Buenos Aires, Max Rocca, was indulging his hobby of poring over Landsat images online, when he noticed something unusual.  There is a river in Colombia called the Vichada which travels through miles of dense jungle before finally reaching the Orinoco.  For most of its course, the Vichada travels in a very predictable way, following the natural shape of the land.  Max Rocca had some training as a geologist, and he could tell where the path of the Vichada River should be in that landscape.  For most of the river’s course, he was absolutely right.  Only at one point did it deviate from the expected course, and that was where it turned at almost a right angle, traced a perfect semicircle through the jungle, and then returned to its former path.

Apparently there was a semi-circular feature on the land at that point, which had never been found before because the jungle growth obscured its outline.  Rocca knew it shouldn’t be there.  There was nothing in the normal seismic and erosional forces shaping this landscape that should have made a perfectly round depression there.

Further investigation showed that the crook in the Vichada River was following a ridge along one side of a circular depression 50 kilometers wide.  A shallow depression surrounded by a ridge of hills is the classic signature of an impact crater, and this was the biggest one every found in South America, 50 kilometers wide.

While Mr. Rocca certainly deserves kudos for his discovery, such features are not rare.  One truly spectacular example is Vredefort Crater in South Africa, which at 300 kilometers wide, is the largest confirmed impact crater on Earth.  (The Wilkes Land Crater in Antarctica is even larger at 500 km., but has not yet been confirmed to be an impact crater.)   Luckily, this event occurred some two billion years ago.  If such an impact happened today, it would induce an “impact winter” effect that would disrupt agriculture on a global scale, resulting in widespread famine and the probable extinction of many of the lifeforms on the planet- especially big ones at the top of the food chain (that’s us).

Of course, the situation is much better now than it was back then, because many of the rocks that were whizzing around two billion years ago have already hit something, but there are still plenty of rocks flying around the sun that are big enough to cause vast destruction.  When you consider the consequences of a single event of the magnitude of Vredefort or even the Vichada impact, it is impossible to ignore the threat.

With this in mind, there has been a lot of very serious discussion in recent years about what we can do if an asteroid or comet is found to be on a collision course with Earth.

The issue is being addressed by various organizations around the world, some associated with specific national governments and others of an international nature.  In 1998, NASA established its Near-Earth Object Program and set a goal of locating at least 90 percent of the estimated 2,000 asteroids and comets larger than one kilometer that approach Earth by the end of the following decade.  Unfortunately, it is now 2010 and this goal has still not been reached, but it probably will be realized in the next few years (see the article on the WISE space probe at this site).

Despite the fact that it has had to revise its original timetable, the NEOP is still alive and well.  In a 2007 report to Congress, NASA refined the goal of the project to the mapping of all bodies larger than 140 meters across whose orbits pass within .05 AU of Earth’s orbit.  At that time, the date of completion was estimated to be 2020.

In its web page about the establishment of this organization, NASA points out that the detection of NEOs also has a possible good side.  We now know that comets and asteroids are rich in substances that will prove useful to future space exploration efforts.  One of the most important of these is water, which exists in frozen form on many of the small bodies of the solar system.  In addition to its obvious usefulness for human consumption, water can be processed to yield oxygen and hydrogen, which also have multiple uses.  Besides this, there may be metals and minerals on some of these bodies that can be mined by future explorers.

The United Nations started an organization in 2001 called Action Team-14, which is dedicated to international discussions of the NEO issue.

This is all good, but it does raise an obvious question: when we find a NEO that is clearly going to impact Earth, what can we do about it?  Bear in mind that if we just shoot a missile at the thing, it will only make matters worse by creating a multitude of smaller pieces, all of which would follow roughly the same path as the parent body.  That would be turning a cannonball into buckshot- not a good idea.

Recent scientific findings have shown just how likely such an outcome would be.  We now know that “rubble piles” are very common in the solar system- see the article at this site about Mars’ moon, Phobos.  These are groups of rocks that stick to each other because of their slight gravitation, but are not actually attached.  If nothing happens to separate these rocks, they might stay together for billions of years; but if something hits them and jostles them apart- say, a missile fired by foolish little germs on some nearby planet- then they could fly apart very easily, and the buckshot analogy would be quite appropriate.

In its 2007 report to Congress, NASA listed different techniques that might be used to deflect a NEO that is on a collision course with Earth, and assessed the potential effectiveness of each one.  Because of the rubble pile problem, they immediately dismissed any idea of detonating an explosive on or under the surface of the body.  However, the report did propose an alternative: bring a nuclear device close to the NEO- but not too close- and set it off.  The force of the blast would nudge the NEO into a different orbit, but if you positioned the explosion right, it might not blow the object to pieces.

What we do depends, to some extent, on how much time we have to get to know our intruder.  In a best-case scenario, we would spot the object some years before it was to make impact.  Then we would be able to send an unmanned probe to study the threatening object.  By transmitting a continuous radio signal during a flyby of the body, the probe would allow Earth-based scientists to measure the Doppler shift of the signal, and calculate the body’s mass.  This would give us a pretty good idea of whether we were dealing with a rubble pile or not.  (As we saw in our Phobos article, rubble pile objects tend to have very low gravity because so much of their interior is empty space.)  If it turns out that we are dealing with a solid body rather than a rubble pile, our troubles are over (almost).  NASA estimates that for such a body, the best approach would be to shoot a non-explosive impactor, or more likely a series of them, at the body and knock it into a new orbit like an oversized pool ball.

Various “slow push” techniques have been proposed.  One of these is to find another asteroid and modify its orbit so that it acts as a tugboat, pulling the threatening object into a new orbit.  Another idea is to put down a robot lander which would actually mine rock from the body and fire it off in high-velocity “bullets,” in effect turning the NEO into a rocket.  Another idea is to send a spacecraft to rendezvous with the NEO and spray-paint it with some coloring agent which would make one side brighter than the other, so that radiation from sun-heated material would provide a small thrust.

One particularly novel proposal has come from America’s Planetary Society: mirror bees.  These are small, unmanned craft that use mirrors to focus sunlight on the NEO, causing material to boil off and create jets which, if carefully positioned, could change its orbit.  Alternatively, they might use lasers rather than mirrors.

The 2007 Congressional report said that while slow push techniques would work in theory, they could only be used if we had plenty of warning, since they all involve getting spacecraft to the object and performing operations that would take some time to be effective.  If we only have short warning- which is likely, unfortunately- then a stand-off nuclear explosion is probably our best bet.

The report also pointed out that up to 80 percent of NEOs might be in orbits that could not be attained by current launch vehicles, which would mean that new launchers would need to be developed.  Even then, it would be necessary to use gravity-assist maneuvers to the fullest advantage to reach some of them.

So the bad news is, if it happens, we’re in big trouble.  The good news is, at least the governments and other institutions of the world are aware of the problem, and are trying to do something about it.  These discussions have yielded some good ideas, but now those ideas must be acted on.  Our planet has been pounded many times before, and each time, many species became extinct as a result.  If we are lucky, maybe it will be different next time.

Sources:

Lendroth, Susan: Press Release- “Saving Earth One Asteroid at a Time” at the website of the Planetary Society:  planetary.org/about/press/releases/2010/0212_Saving_Earth_One_Asteroid_at_a_Time.html

Alexander, Amir: “Project: Asteroids- the Potential Threat” at the website of the Planetary Society:  planetary.org/programs/projects/targetearth/20100213.html

Projects: “Mirror Bees: Planetary Defense” at the website of the Planetary Society:  planetary.org/programs/projects/mirrorbees/

Murrill, Mary Beth and Whalen, Mark: “JPL Will Establish Near-Earth boject Program Office for NASA” at the NASA website:  neo.jpl.nasa.gov/program/neo.html

“Near-Earth Object Survey and Deflection Analysis of Alternatives” (report to Congress, March 2007):  neo.jpl.nasa.gov/neo/report2007.html

Vredefort Crater entry at Wikipedia:  wikipedia.org/wiki/Vredefort_crater

Even before they were launched, these three missions were successes. Mars Express, Venus Express and Rosetta were all built using the same design and many of the same data-gathering instruments. The same facilities were used to assemble the probes, and even many of the same people worked on all three projects. By using this strategy, the ESA was able to greatly reduce the amount of time and expense required to launch the missions.

But at first, Rosetta had a troubled childhood. It was originally approved in November 1993, and the destination was to be the comet 46 P/Wirtanen- but the project ran into delays and was not able to make that destination. Preparations continued with a new goal: comet 67 P/Churyumov-Gerasimenko. The new itinerary was an ambitious 10-year journey that would include two asteroid flybys: 2867 Steins in 2008 and 21 Lutetia in 2010.

This was the mission that finally made it into space on March 2, 2004, launched on an Ariane-5G rocket from Kourou, French Guiana. After that, the probe spent almost four years modifying its orbit by making two passes near Earth, and one near Mars. This put it on course for its first destination, asteroid 2867 Steins.

This was our first chance to get a close-up look at a rare kind of asteroid, the E-type. These bodies are thought to be fragments of larger asteroids that fragmented. They are highly reflective, with a featureless flat spectrum, and are thought to be the source of a type of meteorite called Aubrites. They are greatly outnumbered by other types of asteroids, mainly the M-types. While other probes had obtained pictures of eight asteroids, none of them was an E-type. As Rosetta approached 2867 Steins, the planetary scientists were keenly anticipating their first peek at one of these rare bodies.

The flyby took place flawlessly on September 5, 2008. The closest approach was 800 kilometers, and the relative velocity was 8.62 km/sec. Rosetta immediately confirmed the calculations of ground-based astronomers by affirming that 2867 Steins rotates once every 6.05 hours. The probe took some beautiful, clear pictures of the asteroid, imaging about 60 per cent of its surface. While the pictures were in color, 2867 Steins still looked gray; there was no significant color variation over its surface. Rosetta measured the asteroid’s albedo (reflectivity) and found it to be .4, meaning that it reflected about 40 per cent of the sunlight hitting it. (This is about four times as reflective as Earth’s moon.)

Steins is shaped like a child’s top: rounded on “top,” pointed on the “bottom.” The rounded end is dominated by a huge impact crater, 2.1 kilometers in diameter. Running down the side of the asteroid is a row of seven circular indentations. While these look like impact craters, their similar size and shape, and the fact that they are in a row, would seem to indicate that there is a fracture along that line, and the indentations are actually collapsed pits where dust has settled into the crack. There is also a similar groove along the other side of the asteroid, which may be the same fracture running completely through the body.

The surface features of Steins can be used to make inferences about its history. Its surface is not saturated with impact craters; in other words, there is some empty space visible between them. But we know that the early solar system was a violent place, with many impacts occurring frequently, so we would expect that an asteroid would be completely covered with impact craters. If we find an asteroid that doesn’t look like that, we must assume that something happened to erase the older craters. When looking for a likely cause of this phenomenon on Steins, our attention is immediately drawn to that 2.1-kilometer crater on its top. This is a puzzle, because the impact was so great, it should have shattered a solid body. Normally, if you take a solid rock that’s about 6 km wide and hit it with another rock that’s also of considerable size, they should both split into lots of little fragments.

The conclusion is inescapable: 2867 Steins was never a solid body. It’s a “rock pile,” a collection of fragments held loosely together by their mutual gravitation. When the big impact happened, these fragments were shifted around; some of them probably even flew away and then came back and re-collided with the larger body. Since the asteroid itself was the greatest source of gravity nearby, all the pieces eventually settled back together. The crater from the big impact was so huge, it was still recognizable after the shift- but any smaller craters were completely obliterated. Except for that big crater, Steins got a completely fresh surface, and any smaller craters that we see on it now have occurred since then.

So now we have another portrait of an asteroid, and we know something about its past. Before now, this type of body was an abstraction that existed only on the pages of astronomy textbooks. Now it is a real object that we can see and study. ESA has posted a video of the approach to Steins, and the sight of this little jewel-like object spinning out of the darkness is truly inspiring.

And Rosetta hasn’t even reached its destination yet! This is a really ambitious project, and the hits just keep on coming. In November of 2009, Rosetta modified its course by flying past Earth one more time, which put it on course for the asteroid 21 Lutetia. That encounter will happen in July of this year, and we will gain another asteroid for our photo gallery. These encounters always give us some interesting science, and this one will certainly be no exception.

After this, the probe will go into a period of hibernation. When it wakes up, it will be at it final destination, the comet 67P/Churyumov-Gerasimenko. If all goes well, the probe will go into orbit around the comet and put down a lander, which will anchor itself by shooting harpoons into the comet’s surface. The lander and the probe will stay with the comet through its entire approach to the sun, observing the changes that occur as it heats up and begins to give off the gasses that form the comet’s “tail.” If this is successful, we will finally know in detail exactly what happens to a comet as it approaches the sun.

The show is just starting! Watch for updates at this website.

Sources:

Rosetta homepage at the website of the european Space Agency: sci.esa.int/science-e/www/area/index.cfm?fareaid=13

Space Topics: Rosetta at the website of the Planetary Society: planetary.org/explore/topics/rosetta/

Rosetta: the United States’ Contribution at the NASA website: search.nasa.gov/search/search.jsp?nasaInclude=rosetta+comet+mission

The New Frontiers program came about following a study in 2001 which was conducted to look at the state of solar system exploration at that time and identify priorities for continued exploration during the 10 year period 2003 to 2013. The study identified five medium class missions that were considered of importance and the New Frontiers program was set up to examine and implement these.

The first mission launched was named New Horizons and its goal is to visit and explore Pluto. It will also visit one or more Kuiper Belt objects during the mission. New Horizons was launched in January 2006 and is scheduled to reach its destination by July 2015. The second New Frontiers mission is named Juno and has been designed to conduct an in-depth study of Jupiter. It is currently scheduled for launch in August 2011. At the end of December 2009 NASA announced that three candidates had been chosen for the third New Frontiers program and these include some exciting possibilities for solar system exploration.

The first potential candidate is named the Sunrise and Atmosphere Geochemical Explorer (SAGE) and would comprise a mission to Venus. On arrival it would release a probe into the atmosphere of the planet which would undertake extensive measurements as it descended to the surface of Venus. Upon landing the probe would conduct studies to assess the composition and mineralogy of the surface material.

The second candidate is called the Origins Spectral Interpretation Resource Identification Security Regolith Explorer or Osiris-Rex for short. This mission would be designed to travel to and orbit an asteroid. Extensive measurements of the asteroid would be taken while the spacecraft was in orbit around it. Samples would then be collected from the surface of the asteroid and these would be returned to Earth. These samples would be used to assist in the study of the formation of the solar system and the origins of the molecules necessary for life.

The third candidate would send a spacecraft to land in an area near the south pole of the moon which would collect lunar material and return it to Earth. This mission is known as Moonrise: Lunar South Pole – Aitken Basin Sample Return Mission. The returned lunar sample would be used to help gain an insight into the early history of the Earth-moon system.

Each of the candidates will now have around a year to complete a detailed concept study which is required to consider the feasibility of implementation, the costs involved and technical plans for carrying out and completing the mission. The teams will receive approximately $3.3 million to undertake the concept study and it is currently proposed that selection of the winning candidate will be made in mid 2011. Planning and preparation for the chosen mission would then take around seven years and the spacecraft has to be ready for launch by no later than the end of December 2018.

Each of the missions represents an opportunity for further study of a celestial body and the winning candidate is sure to advance our knowledge of the solar system. All three are potentially exciting opportunities to learn something new and any one of them would provide scientists with a rich source of data. Only time will tell which of the candidates will be successful and for now the three teams have a year of hard work ahead of them.

HAYABUSA was launched on May 9, 2003 on an M-V-5 launch vehicle from Uchinoura Space Center on Kyushu Island, Japan. About a year later, the probe modified its orbit by performing a flyby of Earth, and was sent on a trajectory for its destination. It arrived at Itokawa on September 12, 2005.

It was a perilous journey. Along the way, HAYABUSA had to endure two solar flares, one of which damaged its solar panels, resulting in a delay in arrival. Despite the problems, the mission was a technological success, premiering an array of new devices that will also be used on future space missions. The craft is a beautiful piece of equipment, featuring four ion drive propulsion units and an autonomous guidance system allowing the probe to guide itself without directions from Earth. Its flyby of Earth was the first such maneuver to be achieved using only ion drive as the propulsion.

(For the rest of this article, you must bear in mind that there was a 30-minute signal delay, so the events that are related here in a few paragraphs actually took place over many worried hours, with much nail-biting by the mission control crew.)

So far, so good. HAYABUSA had arrived a little battered, but still capable of performing its mission. It made observations of the asteroid from a few kilometers out. (Itokawa looks a bit like a cucumber: elongated and slightly bent, with little lumps here and there on its surface.) The next part of the mission was to deploy a small hopping robot to rove over the asteroid’s surface. On rough terrain, hopping is sometimes a better way to get around than rolling. It was hoped that this little device would be able to get to places that the larger unit couldn’t.

Unfortunately, this part of the mission was a failure. A technical malfunction caused the hopper to fire in the wrong direction, missing the asteroid completely. It’s still out there somewhere, whizzing around the sun: an artificial asteroid. That was a disappointment, but the main part of the mission was still to come. HAYABUSA prepared for its landing on the surface of Itokawa.

At this point, there was a malfunction that almost ended the mission prematurely. HAYABUSA made two landing attempts, and on the second one, a leak developed in a fluid line within the probe, causing a cascade of damage. After that, there was a period of confusion.

The probe continued to approach the asteroid. The moment of landing came and went, and the probe kept signaling that it was descending. Why was it still descending? Had it missed the asteroid completely, or was the signal simply incorrect? The mission control team decided to give the probe instructions for an emergency ascent in the direction of Earth. It was a gamble, since they were not sure of the status of their probe and were not even certain if it could respond, but it was their only chance.

To their enormous relief, it worked. Communication was reestablished with the probe, which sent an update relating the exact sequence of events:

The first landing attempt was aborted by the probe itself, because it detected an obstacle during the descent and recognized it as a danger. On the second landing attempt, apparently the signal indicating that the probe was still descending after the expected landing time was incorrect. The landing was successful, and the probe remained on the surface of the asteroid for about half an hour. The probe then lifted off from the asteroid.

It was at this point that the leak in the fluid line had developed, resulting in a period of signal loss. During this time, the probe’s onboard computer had rebooted once, causing the loss of all data that was stored at that time. This left the central question unanswered: did HAYABUSA successfully collect its sample of asteroid dust? The team members pored over their data, and there were conflicting press reports which first indicated that the sample had been taken, then that it had not.

The plan had been for HAYABUSA to fire one or two pellets into the ground, throwing up a plume of dust which would be captured and stored in the probe’s sample container. In examining the data from the probe, the scientists were unable to determine if this had been carried out. However, it was ascertained that during the 30 minutes that HAYABUSA was on Itokawa, its sample collector was open and in contact with the ground. It is hoped that even if the pellets were not fired as planned, some dust from the surface may have been disturbed by the landing and drifted into the container. Even a microscopic amount would be of enormous scientific importance.

The problems were not over for HAYABUSA. A malfunction developed in the craft’s ion drive, raising the possibility that it might not be able to put itself into orbit for return to Earth. (We can guess that this may be related to the original fluid leak.) In a heroic save, the team managed to link parts of two of the craft’s four ion engines, thus achieving the thrust of one engine. The reduction in thrust would delay the probe’s return to Earth, originally planned for 2007, until June of 2010.

That day is coming in just a few months now, and provided that the probe’s return to Earth is successful, we will finally learn if it contains the dust of an asteroid. Even if it doesn’t, the Japan Aeronautical Exploration Agency has earned praise from the scientific community for their heroic and ingenious efforts in overcoming the many obstacles that this mission faced. Regardless of the result of the HAYABUSA mission, Japan has suddenly moved into the forefront of space exploration.

Watch for an update at this site when HAYABUSA returns to Earth in June.

Sources:

Website of the Japan Aerospace Exploration Agency (JAXA): jaxa.jp/projects/sat/muses_c/index_e.html

Current Status of the Asteroid Explorer HAYABUSA in Space Daily: Your Portal to Space, February 6, 2009: spacedaily.com/reports/Current_Status_Of_The_Asteroid_Explorer_Hayabusa_999.html

Space Topics: HAYABUSA (Muses-C) at website of the Planetary Society: planetary.org/explore/topics/hayabusa/

Cain, Fraser: HAYABUSA Successfully Collects an Asteroid Sample in Universe Today: universetoday.com/2005/11/29/hayabusa-successfully-collects-an-asteroid-sample/

The protoplanets are baby planets whose development was stopped by the gravity of Jupiter, which disturbed the dust in that region and prevented it from forming into full-size planets. What was left were small bodies that could have been the cores of larger planets, if Jupiter hadn’t been there. It is thought that Earth, Venus and Mars started from similar bodies, but continued their evolution into true planets. So the protoplanets are like snapshots from the early history of the solar system, frozen in perpetual babyhood, and it is hoped that by studying them, scientists will be able to learn something about the conditions under which they were formed. Another objective of the mission is to determine the nature of the building blocks from which the terrestrial planets formed, thus increasing our understanding of the process. A third objective is to contrast two bodies which seem to have followed very different paths in their development, in an attempt to understand the evolutionary processes involved.

The mission is timely because astronomers are beginning to detect planetary systems around other stars, and in the near future we should be able to answer one of the most fundamental questions of space exploration: is our solar system typical, or unusual? Are there other planetary systems out there that are similar to ours? If so, why? If not, why not? Understanding the processes that form such systems is obviously fundamental to answering these questions.

Ceres is the largest of the asteroids. It was the first to be discovered, found on New Year’s Day, 1801 by Giuseppe Piazzi of the Palermo Observatory. Its year is 4.6 times as long as Earth’s, and it has a diameter of about 960 km. (600 miles.) Vesta is the brightest of the asteroids and the only one that is ever visible with the naked eye. It was discovered on March 29, 1807 by Heinrich Olbers. Its year is 3.6 terrestrial years long, and it has a diameter of about 520 km. (320 miles.)

Simply giving the diameter of these bodies is a bit misleading, since they are not flat landforms such as we are used to here on Earth, but three-dimensional objects. While many asteroids are really just pebbles whizzing through space, Ceres and Vesta are big enough to be considered true worlds. To date, the largest asteroid to be approached by a space probe is Mathilde, which was studied by the NEAR-Shoemaker probe in 1997. That asteroid had a very irregular shape, with its largest dimension being about 66 km. (41 miles.) Compare that to the size of Ceres and Vesta, and it becomes obvious that they really are worlds. Vesta has a surface area more than three times that of Arizona, while Ceres’ surface is as big as Alaska, Texas and California combined. Ceres is so large that it may have a wispy atmosphere, and there is even the possibility that it may have permanently frozen polar caps composed of water frost.

Dawn’s ambitious itinerary, with all the course adjustments that it involves, would not be possible with old-style chemical propulsion. Dawn was first lifted into space by a Delta rocket, but since leaving that rocket, it has been relying on its ion drive. This is an advancement that was anticipated by science fiction writers for many years, and it works just as well in real life as it did in fiction. First used to great advantage by the Deep Space 1 probe, ion drive allows far greater flexibility and maneuverability than a chemical rocket would. Whereas chemical rockets are able to deliver large amounts of thrust for a short time, the ion drive is able to deliver lower thrust for a much longer time. The system is powered by solar panels. The power from these ionizes the fuel (xenon) and then accelerates it with an electric field between two grids. The resulting jet shoots out the rear of the engine at a speed of 60,000 miles per hour.

The idea of the ion drive has had a long history. Hermann Oberth, one of the pioneers of rocketry, proposed such a system in the 1930′s, but because chemical rockets were easier to design, the development of rocketry went in that direction instead. Now the technology has finally caught up with the vision, and we see that Oberth was right: this is a reliable and efficient propulsion system. Given its excellent performance so far, it will certainly be used on many spacecraft in the future.

In more ways than one, Dawn is the fulfillment of dreams. Many a science fiction story has been written about the settlement and mining of the asteroid belt. With the Dawn mission, we are taking a step toward that dream.

Sources:
Website of the Jet Propulsion Laboratory, California Institute of Technology dawn.jpl.nasa.gov/

Dawn: a Journey to the Begining of the Solar System ssc.igpp.ucla.edu/dawn/

Ambrosiano, Nancy: Dawn Space Mission is a Go in Los Alamos National Laboratory News Bulletin lanl.gov/news/index.php/fuseaction/nb.story/story_id/11526

Dawn Spacecraft at Aerospaceguide.net aerospaceguide.net/spacecraft/dawn.html

Many people may have missed the news but an asteroid was detected passing less than 9000 miles from the Earth on Friday 6 November and it was only 15 hours before this happened that the comet was actually detected. The asteroid was first picked up by researchers at the University of Arizona as part of their Catalina Sky Survey and following this was detected by the Minor Planet Centre in Cambridge Massachusetts. The asteroid was then picked up by the National Aeronautics and Space Administration (NASA) and its trajectory plotted.

The 23 foot wide asteroid has been christened 2009 VA and at its closest it was only 8700 miles from the Earth. This is 30 times closer than the Moon which lies approximately 250,000 miles from the Earth and it was the third closest approach of an asteroid ever recorded. However it is not considered that the asteroid would have made much of an impact and in actual fact it probably would have burned up in the Earth’s atmosphere long before it reached the ground.

However the more worrying aspect of the story is the fact that it was only detected 15 hours before it passed the Earth. This demonstrates that there are still objects out there that we know little about and shows how close they can approach before actually being detected. Although 2009 VA actually posed little threat, a larger asteroid could have potentially devastating consequences if it were to collide with planet Earth.

NASA was tasked by Congress with identifying at least 90% of the asteroids that are considered to pose a threat to our planet by 2020. They were assigned the task in 2005 and initially estimated there were around 20,000 dangerous comets and asteroids, with those that are 460 feet or greater in size being considered a risk. To date scientists have accurately located around 6000 of these and the scheme which is known as the Near-Earth Object Program continues.

However the passing of 2009 VA shows how difficult this task will be. For an asteroid to get so close to the Earth without being detected is not something that should be taken lightly. NASA monitored a 100 foot asteroid in March this year as it passed around 45,000 miles from the Earth. An asteroid of similar size crashed into planet Earth in 1908 although it landed in a remote part of Siberia. The impact however devastated an area 1,200 square miles in size and if such an object landed near an area of dense population there would be severe consequences.

The NASA project is therefore important and if an early warning of an imminent strike was given this could greatly reduce the human consequences involved. 2009 VA was a lesson that the task of identifying near earth comets and asteroids is not an easy one although the hunt will go on.

This meteor shower is one of the most showy and dazzling of them all in the northern hemisphere. For over a hundred and fifty years this event has been known to be very active displaying at least one streaking meteor every thirty seconds. In other past occurrences it created sixty meteors per hour. On the average, one hundred meteors per hour radiate throughout the sky. This is known as the Zenith Hourly Rate (ZHR).

The winter December sky will provide an excellent chance to experience the meteor event. Visibility will be enhanced by a new moon ensuring that zenith hour rate is seen. Originating from the Gemini constellation and scattering relatively slowly across the sky provides viewers a chance to see the trails with the unaided eye. These shooting star trails last a number of seconds and be seen in varying colors. In the northern latitudes it can be visible in the not-to-late evenings. This is perfect timing for star parties, astrophotography and even family viewing.
Discovery of the Geminids
Three astronomers all working independently in 1862 are credited for the discovery of the Geminids meteor shower. The first noted was R. P. Greg (England), secondly B. V. Marsh (United States.) and lastly A.C. Twining (United States). More sightings and reports came during 1863 and 1864.

It wasn’t until 1983 that the origin of the Geminids meteor shower was uncovered. Once again, three astronomers are given the credit. Two for identifying an asteroid and one for researching and associating the orbit to the meteor shower. Simon Green and John Davies identified the asteroid 3200 Phaethon. Fred Whipple noted the asteroid’s orbit and associated it to the meteor shower.

What is still a mystery about the Geminids meteor shower? Even though 3200 Phaethon has been identified as an asteroid, there is a possibility that it could be a dormant comet. The question arose when a photographic density study was conducted and the results proved to be less dense than asteroids.

Asteroid or comet, 3200 Phaethon has been officially linked to be the origin of the Geminids meteor shower. The meteor shower happens every December and this year gives us a great chance to watch.

The art/science of studying the stars was engaged by several ancient populations like Maya, Incas, Egyptians and Greeks, and soon grew in importance to the point where those who practiced it were highly regarded and respected in their own society. The reason for this is evident: this science could provide, even from its first, rudimentary structure, an explanation to phenomena strictly connected to their life, such as the alternating of day and night or the cycle of seasons, and provided an essential instrument for activities such as agriculture and navigation.

The history of Astronomy is in part — from its origins to the invention of the telescope by Galileo Galilei, in 1610 — also the history of astrology. In prehistoric ages, the most advanced tribes were familiar with the motion and trajectories of just a few, visible objects like the sun, the moon and some of the brightest stars. The most commonly cited example of such knowledge is the Stonehenge complex, residing in Great Britain, which is thought to have served as a monumental calendar.

Chinese astronomy was born before 2000 BC and is still cited nowadays for its great tradition of carefully, a-critic documentation. From the documents in our possession we know that in their time they were already aware of events such as the passage of comets, or even the explosion of a Supernova star.

A few civilizations in central America also reached astonishing results, but unfortunately they didn’t manage to share they knowledge with other populations. Maya and Inca tribes would often build pyramids and temples, which were devoted to the Gods of the Sky. Their religion was strictly related to the planet Venus and, based on estimations of its motions, they managed to create an incredibly precise astronomical calendar, finding out, among other things, that the planet would accomplish five complete orbital revolutions in the time span of exactly 584 days.

Babylonians soon showed exceptional knowledge in the matter of astronomy, which would later be inherited by Egyptians and Indians. In their case, the desire to perfect this science at all costs came, rather than an actual need, from skeptical reasons that linked the motion of stars and planets to good or bad luck (solar and lunar eclipses were thought to bring extremely bad luck, and this conception would persist until relatively recent times). Even lacking any sort of precise instrumentation, Babylonians managed to find out many things about the apparent motion of planets, basing their observation on the position of a few bright stars on the sky: they therefore discovered the orbital revolution time of many planets, among which Venus, Mars, Jupiter and Saturn, only mistaking by a few days, and reporting the results of their calculations on special tables, most of which are well-preserved and can still be seen now in astronomical museums.

Egyptians’ immense and astonishing knowledge regarding astronomy relies, once more, on their ability to forge precise calendars describing the motion of stars and planets. As their life cycle was strictly linked to that of the Nile river, astronomy was given a central role by this society from the very beginning. Around 3000 BC, Egyptians were already used to dividing their day and night time in regular intervals of 12 parts each: day time would be measured by sundials, while night time would be measured by observing the relative position of 24 bright stars. Measuring this way, their ‘hours’ would have a different duration depending on the season, but still averaging 60 minutes each.

It was only with Greek astronomy, though, that a stress was posed on developing theories that would explain the birth of the Universe and its mechanics: Anaximander thought the planet Earth was a cylinder at the center of the Universe, while the stars would rotate around it in all directions; Plato had at a first time a theory, extremely advanced for its time, that put the Sun at the center of the Universe, but he later withdrew it to favor an Earth-centric theory similar to that of Anaximander; Eudoxus of Cnidus, finally, advanced a theory that was later approved by Aristotle, according to which the Universe was made of concentric spheres, rotating one inside another, where the Earth would be in the center.

The Aristotle conception of the structure of the universe was meant to last, with minimal variations, until the year 1500 AD, when Nicolaus Copernicus — which many consider the father of modern astronomy — advanced a theory that put the Earth orbiting in perfect circles around the Sun, together with all the other planets: this approach could in fact solve many of the contradictions that those who supported Aristotle had to face. A few decades later, John Kepler refused yet another innovative model of the universe from his mentor Tycho Brahe, and later became famous for formulating the three laws of star mechanics that were named after him, which are considered valid still nowadays.

In 1610, Galileo Galilei invented the telescope, after a long period of research and experimentation. As soon as he pointed it at the stars, a never seen before universe appeared in front of his eyes: the Moon had a surface full of craters, Jupiter was surrounded by four satellites, while the Milky Way suddenly appeared as nothing but a huge mass of countless stars. In 1632, after publishing his book ‘Dialogo sopra i due massimi sistemi del mondo’ [On the main two models of the Universe] in which he was openly exposing the results of his observations, he was forced by the Catholic Church to abjure not having made those discoveries.

A few decades later, while researching innovative techniques to build more and more powerful telescopes, an important debate took place between the scientist Huygens and Newton over the nature of light: the first said it was a wave, while the second thought it was made of physical ‘atoms’ (photons). The debate that was destined to be solved once and for all just a few decades ago (light is, indeed, both a wave and a physical object). Huygens studied advanced optics as well, and managed to build a telescope that could noticeably minimize the chromatic aberration in observations, which led him to discover Saturn’s rings and its moon, Titanus.

Just a few years later, Cassini and Romer found out that phenomena such as solar eclipses would happen just several minutes after they were expected: this led them to think that light could actually travel at a finite although extremely high speed, rather than to an infinite speed: their estimation put the speed of light at 230,000 km per hour (the actual speed of light is 300,000 km/h).

Starting from the 19th century, following the Industrial Revolution, the continuous development of innovative techniques and instruments for the observation of the sky led to a series of discoveries that quickly contributed to our knowledge. Nowadays, the main purpose of astronomy is to study the life cycle of stars and galaxies, the origin and future of the Universe, obscure objects like pulsars and black holes, and methods to measure interstellar distances with increased precision.

We would like to thank you for your participation in the 2012-Comet.com newsletter! This month we would like to address two common email messages that we receive from time to time:

“According to Jesus, no man or woman knows the
day nor the hour when the end will come.”

This is our response:

We know that our website is more or less considered an end of the world website. However; we really do not believe that the end date is December 21, 2012. We believe that a Comet will hit the earth in 2012. This event may signal the beginning of the end times. We have always been curious of what it would take for the world to start using one currency. An event like this would cause so much chaos that we might need one strong leader to take control of all countries. This event will probably wipe out most of the population, but not all. What would it take for all of the countries in the world to use one currency? Could this event be the beginning of the end? We don’t know. However; if the Bible Codes are true, they specifically state: 2012 Comet

We received another email from a mother whose children stumbled upon our website. The children said: “Mommy is this true? We don’t want to die.”

Our response would be that you do not let your children watch the Discovery Channel, the History Channel or the National Geographic Channel. All of these channels talk regularly about 2012 and mention the Bible Code prediction quite frequently.

UFO News:

Blossom GoodChild predicted that a large UFO would appear over a major city two days ago. Well it looks like she was mistaken. Currently there is a nasty video in the Daily Videos section expressing some anger towards Blossom GoodChild. Who knows why her prediction did not come true or if it was a money making scheme.

Good News:

It appears that scientists have created another idea for directing comets and asteroids out of the earths orbit. The latest idea is to fly in a sun reflecting device and burn a hole in the comet or asteroid. This would then hopefully cause the rock to change course and miss the earth entirely. We are excited about this development and hope that scientists will continue brain storming on different ways to save the planet.

This asteroid passing did not get a lot of media coverage, but it was definitely a close call to say the least. This type of activity in our solar system is just an example of how we could all go to sleep one night and not wake-up the next morning.

What interests us the most is that an amateur astronomer found this 40 yard sized asteroid and not one of the big telescopes. It is reported that about every 100 hundreds years we have a Tunguska asteroid hit. Below is a video on what happened when this small asteroid hit in Siberia:

source: http://news.bbc.co.uk/2/hi/science/nature/7921279.stm