Great Image: Colliding Spiral Galaxies

The image above is from NASA's Astronomy Picture of the Day website and represents the combination of galaxies, a process that will continue for billions of years.  Our own Milky Way galaxy has abosorbed other galaxies in the past and is expected to have more collisions in the future.  Here is the story for the image above:

Billions of years from now, only one of these two galaxies will remain. Until then, spiral galaxies NGC 2207 and IC 2163 will slowly pull each other apart, creating tides of matter, sheets of shocked gas, lanes of dark dust, bursts of star formation, and streams of cast-away stars. Astronomers predict that NGC 2207, the larger galaxy on the left, will eventually incorporate IC 2163, the smaller galaxy on the right. In the most recent encounter that about peaked 40 million years ago, the smaller galaxy is swinging around counter-clockwise, and is now slightly behind the larger galaxy. The space between stars is so vast that when galaxies collide, the stars in them usually do not collide.

Image Credit: Debra Meloy Elmegreen (Vassar College) et al., and the Hubble Heritage Team (AURA/STScI/NASA)

Opportunity Rover: A Cry for Attention?

With the Curiosity rover getting all of the attention these days, it was only a matter of time before the older Opportunity rover would pull a stunt to let us know she is still there (unlike her sister, Spirit, who is no longer functioning).  The two photos above are 12 days apart as Opportunity explores the Murray Ridge on the rim of Endeavour Crater (see bottom image).  Within that time a new rock appeared on the surface.

CNN and others were quick to report on a doughnut-sized rock that mysteriously appeared on the surface of Mars. The most likely explanation is that Opportunity kicked up the rock while traveling about.  But theories will always abound.  My theory is that Opportunity was getting a little lonely and wanted to let us know she is still working hard after all these years.

Luckily, NASA will hold a press conference later today to discuss the 10 year anniversary of the Opportunity mission on Mars.  The rover arrived on January 24, 2004.  Maybe that was all Opportunity really needed - a little appreciation. 

Note: For more images from Opportunity, visit the NASA Jet Propulsion Laboratory. 

Update:  And now, another cry for attention.  For some odd reason, someone is now suing NASA over the presumably dislodged rock.  A private citizen, Rhawn Joseph, filed a petition January 27th in U.S. District Court in northern California.  In his petition, Mr. Joseph stated,

Any intelligent adult, adolescent, child, chimpanzee, monkey, dog or rodent with even a modicum of curiosity would approach, investigate and closely examine a bowl-shaped structure which appears just a few feet in front of them when 12 days earlier they hadn't noticed it...But not NASA and its rover team who have refused to take even a single close-up photo. 

An interesting approach to science.  And you too still have time to sue NASA for all of the craters and rocks missed by the Apollo crews during their Moon visits many decades ago.  I do not believe there is a statute of limitations on craziness.  

NOVA: A Story About Exoplanets

Earlier this month PBS's NOVA had an good program on exoplanets called Alien Planets Revealed.  You can still view the show on NOVA's website, and here is a quick summary from that same site:

It’s a golden age for planet hunters: NASA's Kepler mission has identified more than 3,500 potential planets orbiting stars beyond our Sun. Some of them, like a planet called Kepler-22b, might even be able to harbor life. How did we come upon this distant planet? Combining startling animation with input from expert astrophysicists and astrobiologists, “Alien Planets Revealed” takes viewers on a journey along with the Kepler telescope. How does the telescope look for planets? How many of these planets are like our Earth? Will any of these planets be suitable for life as we know it? Bringing the creative power of veteran animators together with the latest discoveries in planet-hunting, “Alien Planets Revealed” shows the successes of the Kepler mission, taking us to planets beyond our solar system and providing a glimpse of creatures we might one day encounter.

Sadly, the Kepler space telescope is no longer searching the heavens after a mechanical failure in May 2103, but the wealth of information that it provided between 2009 and 2013 will keep scientists busy for many years to come.  The NOVA program discusses some of the finding, including Kepler 62F, the first promising earth-like planet to be discovered (see NASA artist concept below).  Kepler 62F is about 1,200 lights years away and the program makes it clear that it would take "many million years" for us to get there with our current spacecraft.  Given NASA cannot get a budget one year out, it is unlikely this Congress will be contemplating such missions (though I still vote we send a CODEL - or congressional delegation - on the mission anyway).  

The NOVA program also discusses how about 75 percent of the stars in the galaxy are red dwarves, which means the nature of life around other suns may be quite different from ours based on the light received on the surface of the exoplanets.  Some of the ideas about flora and fauna on these red dwarf exoplanets was pretty interesting. 

Another discussion point was how our own planet's life was nothing but microbes for billions of years, and therefore this is what we should probably suspect in terms of "life" on these exoplanets if there is life at all.  And the idea that intelligent life would evolve on such exoplanets is not a given.  NOVA uses the shark as an example of non-intelligent life staying pretty much the same over 400 million years.  Hence, life may be abundant in the universe without much or any of it being intelligent or at a stage of intelligence that can communicate with us.

After all of that, the program still leaves us with the point that one out of every six stars in our galaxy has an Earth-sized planet orbiting it, which puts the number of Earth-sized planets at about 17 billion for the Milky Way.  That gives us plenty of exoplanets to explore even with all the caveats above. 

Top Image Credit:  Exoplanet Eclipse/Bill Lile, quoted from: http://www.flickr.com/photos/blile59/313907609

A Rocket Tower to Nowhere

At a time when NASA is struggling to find the necessary funds to cover planned space missions, why is the Agency spending $350 million on a tower that is no longer needed?  The A-3 test stand tower at the Stennis Space Center in Mississippi is a piece of pork that local legislators insisted must be completed even though it is designed for rockets that will never be built since they are part of the canceled Constellation program.  Businessweek magazine reported that NASA's inspector general has been highlighting such waste of funds:

Testifying before the House space subcommittee in September, Martin highlighted the A-3 as an example of how lawmakers, looking to keep federal dollars flowing to their states, can block efforts to cut unnecessary spending. “The political context in which NASA operates often impedes its efforts to reduce infrastructure,” he said.

You can find more such stories of wast in the February 2013 NASA IG report, NASA's Efforts to Reduce Unneeded Infrastructure and Facilities. The report noted:

During our fieldwork we identified a variety of facilities at multiple NASA Centers that the Agency was not utilizing or for which Agency officials could not identify a future mission use. These facilities ranged from smaller, low value post-World War II era thermal vacuum chambers to newer rocket test stands that cost several hundred million dollars to construct.

We concluded that previous efforts by NASA to reduce its underutilized facilities have been hindered by: 1) fluctuating and uncertain strategic requirements; 2) Agency culture and business practices; 3) political pressure; and 4) inadequate funding. The combination of these forces has frustrated NASA’s efforts over the years to make meaningful reductions in the size of its real property portfolio. 

Either we want a space program or a jobs program, but trying to do both ties our hands and limits our reach as a nation.  We will always have some level of politics in anything that requires the involvement of Congress, but it may be time to let NASA focus on the future and not be hindered by leftover from the past.

Image Credit:  Bloomberg Businessweek

Extra Life for the International Space Station

The White House recently announced that the International Space Station (ISS), set to be decommissioned in 2020, will now get an extra 4 years of life through 2024.  In the press release, the White House stated:

[The extension] will allow NASA to complete necessary research activities aboard the ISS in support of planned long-duration human missions beyond low-Earth orbit—including our planned human mission to an asteroid by 2025 and to Mars in the 2030s.  NASA has determined that research on ISS is necessary to mitigate fully 21 of the 32 human-health risks anticipated on long-duration missions.  A related critical function of ISS is testing the technologies and spacecraft systems necessary for humans to safely and productively operate in deep space.  Extending ISS until 2024 will give us the necessary time to bring these systems to maturity.

On January 9th, NASA Administrator Charles Bolden reemphasized the role of the ISS in future space endeavors, making the following statement:

NASA is committed to the space station as a long-term platform to enable the utilization of space for global research and development. We’re committed to implementing a unified strategy of deep space exploration, with robotic and human missions to destinations that include near-Earth asteroids, the moon and Mars. And we are committed to our international partnerships and the continued peaceful uses of outer space and unlocking the mysteries of our vast universe.

Of course, Congress will still need to agree.  And at $3 billion a year in maintenance costs, added to the recent scares, will not make this an easy argument.  That said, the station represents a major piece of the American space program and after more than $100 billion in construction over more than a decade, to allow the station to become space junk earlier than necessary would be foolish. 

The extension would also benefit smaller start up firms, such as SpaceX and Orbital Sciences, that are still getting their legs as they build new spacecraft and begin the privatization of space (or at least low Earth orbit).  In fact, earlier today Orbital Sciences' Cygnus capsule successfully docked with the ISS to resupply its occupants.  The only question now is whether we will have space partners down the road.  China is already building its own space station and Russia has been thinking of doing the same. 

Abandoned Astronomy

Like the wrecked Mayan remains one finds centuries later in the Latin American jungle, this Bloomington, Indiana, space observatory represents time moving on even with the most modern of endeavors.  The Knightridge Space Observatory pictured above is a four-ton telescope built in 1936 and 1937.  You can see many more images like this one and the one below (the Pip Ivan Observatory in Ivano-Frankivsk, Ukraine) at io9.

Top Astronomy Stories in 2013

This is the time of year to highlight some of the great discoveries of the last year, and we have plenty to ponder.  CBS news highlights events such as the discovery of the Higgs Boson, life in Antarctic lakes, more evidence of water on Mars, and the Chinese moon landing.  I would add the Indian mission to Mars as another key event.

CNN’s list of 2013 scientific stories included the stray asteroid that hit the Russian city of Chelyabinsk in February 2013 (notice this is a story rather than a discovery, though the people in Russia certainly discovered something new about the risk of life here on the third rock from the sun).

Wired magazine covered both discoveries and stories, with discoveries including estimates that our galaxy may contain about 10 billion Earth-like planets (using data from NASA’s Kepler space telescope).  Top stories included Mars One, the plan to send humans one-way to Mars in 10 years, and the mysterious environment encountered by Voyager 1 at the edge of the Sun’s heliosheath.  Wired also discusses the diminishing availability plutonium-238, which may impact out ability to repeat Voyager-like missions in the future.

Great Image: The Cape of Good Hope

Below is NASA’s Earth Observatory description of this ISS photo:

Nelson Mandela took the long view of South Africa. He saw the potential for prosperity and peace through equality during a time of repression, turmoil, and inequality. In tribute to Mandela, astronaut Chris Hadfield offered up his version of South Africa’s long view.

This photo was taken from the International Space Station on May 9, 2013, looking across the southwestern tip of the country. The image focuses on the mountainous Western Cape, dominated by the Great Escarpment, a 5,000-kilometer long mountain chain that marks the edge of the African plateau. The Cape of Good Hope hooks out from the mainland, with the city of Cape Town coloring the top in cement gray. To the east is Cape Agulhas, the southernmost point of the African continent where the Indian Ocean meets the Atlantic Ocean.

The view from above helps us see the geographic connections that bind humanity together on a single planet. Writing in Wired, Hadfield said: “While I was on the space station, I used Twitter to ask hundreds of thousands of people what they would like me to take a picture of. Resoundingly, the answer was ‘home.’ After millennia of wandering and settling, we are still most curious about how we fit in and how our community looks in the context of the rest of the world.”

Connection is something that Nelson Mandela understood on many levels. Speaking at Mandela’s memorial service on December 10, 2013, President Barack Obama stated: “Mandela understood the ties that bind the human spirit. There is a word in South Africa—Ubuntu—that describes his greatest gift: his recognition that we are all bound together in ways that can be invisible to the eye; that there is a oneness to humanity; that we achieve ourselves by sharing ourselves with others, and caring for those around us.”

As the world pauses to lay Nelson Mandela to rest on December 15, we salute the power of connections.

Recreating the Famous Earthrise

NASA has issued an interesting video that recreates the famous Apollo 8 “Earthrise” photography that occurred this Christmas week 45 years ago.  Updated images from NASA’s Lunar Reconnaissance Orbiter were critical to providing a precise capture of the same angles and shots.  This, plus the old audio clips of the banter between the three astronauts, provides us with a blow-by-blow retelling of the background to this forever-famous Earth image. Think of it as a remake of a great old film that never ceases to amaze.

The Drama is Over, For Now

Luckily, NASA is going into the new year with a functional International Space Station (ISS).  The recent space walks were a success (see the final installation above) and a new ammonia pump is being integrated in the station to ensure proper cooling.  This is not the first nor the last maintenance emergency for the ISS.  Given its aging components, we should expect to see more space walks and part replacement. 

Dueling Versions of Space Safety

With all the drama related to repairs to the International Space Station (ISS), one can see NASA finally trumping Hollywood.  While we do not see space debris tearing the station apart as in Gravity, in this case real lives are a stake on a multi-billion dollar platform miles above our heads.  While both stories fascinate the public, I hope to use this blog (again, after a little time away) to bring together various images and ideas to build a better understanding of space science and our potential future as we use it, hopefully, to improve our future.

Great Image: The Pyramids from Space

The image to the right is from NASA's Earth Observing System Data and Information System (EOSDIS).  It shows the Great Pyramids at Giza on July 25, 2012, as viewed from the International Space Station.  Here is NASA's description of the shot taken by a hand-held Nikon digital camera:

The southeast-facing sides of the pyramids of the pharaohs Khufu, Khafre, and Menkaure are all brightly illuminated by the Sun, while the northwest facing sides are in shadow. This shadowing also highlights smaller, unfinished pyramids to the south of Menkaure’s pyramid and fields of rectangular, flat-roofed mastabas (tombs) to the east and west of Khufu’s pyramid. While not as grand as the pyramids, mastabas were the burial places of prominent people during the time of the ancient pharaohs. To the southeast of Khufu’s pyramid, the head and rear haunches of the Sphinx are also visible (albeit not clearly).

Life on Mars?

While Curiosity has had a few recent problems, it has already had great success with its intended mission.  Last month's rock sample from the Gale Crater indicates Mars could have supported life as far back as 3 billion years ago.  The sample included ingredients to life, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon.  According to a NASA press release,

"A fundamental question for this mission is whether Mars could have supported a habitable environment," said Michael Meyer, lead scientist for NASA's Mars Exploration Program at the agency's headquarters in Washington. "From what we know now, the answer is yes." 

It seems we have answered the $2.5 billion answer (the price tag of Curiosity).  So, what's next?  We know Mars had water and could have supported life.  Unfortunately, Curiosity is not equipped to actually detect life itself, so we may need to wait for another mission to do that.  It would be fascinating to learn that life existed on both Earth and Mars at the same time, or even that there is some relationship between life on each planet with one somehow seeding the other (or being jointly seeded in the same way, via a comet for example).  You can learn more about this mission via a NASA broadcast of a March 12th press conference on the rock analysis.

One of the next questions that needs to be "Can Mars support life in the future?"  We hear of government and private sector plans to visit the Red Planet, but nothing solid.  While the science continues on the surface of Mars, let's hope the planning for a future manned visit continues on the surface of Earth.  We have much to learn and much to do, but we need to keep that question in front of ourselves daily as we move forward with our exploration of space.

Curious Problems on Mars

SpaceX was not the only space mission dealing with problems last week.  The Mars rover Curiosity was also dealing with problems that delayed the mission for more than a week.  It appears a computer glitch in late February caused the rover to switch into safe mode.  Luckily, built-in redundancies were established for this type of scenario. Curiosity switched from Computer A to Computer B while repairs are underway.  Some memory loss was anticipated as a result of the computer problems.

And now a solar storm is approaching Mars, causing NASA to shut down the rover one more time.  Solar radiation may have also been the cause of the earlier computer glitch, so it makes sense to be safe.

Only last month had Curiosity started to collect its first Martian samples by drilling into the planet's surface (see image below), with NASA noting:

"The most advanced planetary robot ever designed is now a fully operating analytical laboratory on Mars," said John Grunsfeld, NASA associate administrator for the agency's Science Mission Directorate. "This is the biggest milestone accomplishment for the Curiosity team since the sky-crane landing last August, another proud day for America." 

Hopefully, the mission will get back on track after these bumps.  

Another Asteroid Heading Our Way

As if last month's asteroid near miss and Russian meteorite was not enough to get the world's attention, we have more asteroids heading our way.  Tomorrow a 330-foot-wide asteroid called 2013 ET will make a near approach to the Earth, missing us by about 600,000 miles (or about 2.5 times the distance from the Earth to the moon).  According to news reports, this large asteroid was first detected on March 3rd, not giving us much time to worry had its trajectory been somewhat different. 

Remember, 2013 ET is twice the size of last month's 2012 DA14, of which NASA stated:

...if another asteroid of a size similar to that of 2012 DA14 (about 150 feet across) were to impact Earth, it would release approximately 2.5 megatons of energy in the atmosphere and would be expected to cause regional devastation. 

Are we facing more risks as time goes by, or are we simply more aware of a scary situation that has always been out there?  I would like to think it is the latter. 

SpaceX: A Scary Mission Ends Successfully

The good new is that on Sunday the SpaceX Dragon successfully attached to the International Space Station (ISS) to resupply the crew.  According to NASA:

Space station Expedition 34 crew members Kevin Ford and Tom Marshburn of NASA used the station's robotic arm to successfully capture Dragon at 5:31 a.m. The capture came one day, 19 hours and 22 minutes after the mission's launch. The station was 253 miles above northern Ukraine.

The bad news is that the Dragon seemed to have problems along the way that SpaceX will need to resolve for future missions.  To recap, about 10 minutes after Friday launch of the Dragon capsule, three of the four sets of rocket thrusters failed to engage.   Here is now SpaceX explained it:

After Dragon separated from Falcon 9’s second stage approximately nine minutes after launch, a minor issue with some of Dragon’s oxidizer tanks was detected. Within a few hours, SpaceX engineers had identified and corrected the issue, normalizing the oxidizer pressure and returning operations to normal. Dragon recomputed its ascent profile as it was designed to and is now on its way to the International Space Station (ISS) with possible arrival on Sunday, just one day past the original timeline.

I am not surprised SpaceX will spin it as a "minor issue," but was it?  Hopefully, NASA and SpaceX will thoroughly investigate the problem.  You may recall that the first resupply mission to the ISS also had an "anomaly" in a rocket engine.  Given the complex nature of such missions, problems such as these are not unheard of.  The key is learning from the problems. And SpaceX's Mr. Musk does not want to do anything to jeopardize future missions with NASA.

In 22 days, the Dragon will return to Earth, bringing back various science experiments being tested on the ISS. Let's hope things are smooth for the rest of the mission.

Elon Musk: Car Trouble

Elon Musk seems to be having much better luck in space than down here on Earth.  While SpaceX has been a great success proving his abilities to service the International Space Station (ISS) with a homemade rocket, his Telsa Motors car enterprise has gotten off to a rocky start. 

Telsa Motors is still recovering from a bad review of its Model S in The New York Times.  On February 8th, John M. Broder wrote an article titled "Stalled Out on Tesla’s Electric Highway" where he listed all of the problems he encountered with the car and charging stations during a drive from Newark, Delaware, to Milford, Connecticut.  Mr. Musk did not take the review very well, noting on his company blog that Telsa Motors was "played for a fool":

When Tesla first approached The New York Times about doing this story, it was supposed to be focused on future advancements in our Supercharger technology. There was no need to write a story about existing Superchargers on the East Coast, as that had already been done by Consumer Reports with no problems! We assumed that the reporter would be fair and impartial, as has been our experience with The New York Times, an organization that prides itself on journalistic integrity. As a result, we did not think to read his past articles and were unaware of his outright disdain for electric cars. We were played for a fool and as a result, let down the cause of electric vehicles. For that, I am deeply sorry.

If Mr. Musk wanted attention for his new car he got it. 

This is just one of many battles being fought by Mr. Musk as he rolls out his cars nationwide.  Last October the Los Angeles Times discussed Telsa Motors struggle to bypass traditional franchise networks and sell directly to customers.  In the article titled "Shock to the System," the South African owner of Telsa Motors questioned the U.S. approach for selling cars:

"Existing franchise dealers have a fundamental conflict of interest between selling gasoline cars," Musk said. "It is impossible for them to explain the advantages of going electric without simultaneously undermining their traditional business."

State automobile dealer associations are now suing Telsa Motors to halt his direct sales.  Again, the feisty Mr. Musk is making a name for himself for himself and his cars. 

With all of this, SpaceX is still on schedule to send a Dragon capsule to the ISS on March 1 for its second resupply mission.  Let's hope no one from The New York Times is on capsule rating the ride. 

Meteorite Damage in Russia

While 2012 DA14 safely passed the earth on Friday, another unexpected rock plummeted to Earth and struck Russia (again) the very same day.  More than 100 years after the Tunguska, Siberia, meteor strike, a new meteor struck Russia in the Chelyabinsk region (see map below).  The two regions are about 3,000 miles apart.

The meteor was estimated to be about 55 feet and weighing approximately 10,000 tons. The incoming explosion released nearly 500 kilotons of energy and early estimates indicate 1,000 people where injured, primarily from broken glass as windows shattered.

According to the Associated Press, 

The explosions broke an estimated 100,000 square meters (more than 1 million square feet) of glass, city officials said.

Chelyabinsk health chief Marina Moskvicheva, said Friday that 985 people in her city had asked for medical assistance. The Interfax news agency quoted her as saying 43 were hospitalized. Athletes at a city sports arena were among those cut up by the flying glass.

NASA stated that such occurrences are to be expected every 30 years or so, and noted that this event and the 2012 DA14 asteroid were unrelated:

"We would expect an event of this magnitude to occur once every 100 years on average," said Paul Chodas of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif. "When you have a fireball of this size we would expect a large number of meteorites to reach the surface and in this case there were probably some large ones."

The trajectory of the Russia meteor was significantly different than the trajectory of the asteroid 2012 DA14, which hours later made its flyby of Earth, making it a completely unrelated object. 
 
It is understandable that people will conflate the two events occurring on the same day.  I would like to know the odds of this event happening.  

In a February 14 editorial in The Wall Street Journal, the authors provided additional estimates on the likelihood of future meteor strikes,

The chance of another Tunguska-size impact somewhere on Earth this century is about 30%. That isn't the likelihood that you will be killed by an asteroid, but rather the odds that you will read a news headline about an asteroid impact of this size somewhere on Earth. Unfortunately, that headline could be about the destruction of a city, as opposed to an unpopulated region of Siberia.

The chance in your lifetime of an even bigger asteroid impact on Earth—with explosive energy of 100 megatons of TNT—is about 1%. Such an impact would deliver many times the explosive energy of all the munitions used in World War II, including the atomic bombs. This risk to humanity is similar to an individual's odds of dying in a car accident.

This was published one day before the meteor struck Russia.  I wonder if the authors would update their estimates today (or turn in their car keys).

How Do We Protect the Milky Way Galaxy from a Collision?

Just one idea from the comic site Saturday Morning Breakfast Cereal:

Asteroids: Post-Valentine's Day Massacre? Not Really

With the pending approach of a large asteroid the day after Valentine's Day, one which will come between us and the moon, it is reasonable to ask if we are prepared.  The asteroid in question is called 2012 DA14, and is about 150 feet across in size and traveling at a speed of 17,450 miles per hour.

NASA scientists have told us that there is nothing to be worried about (I remember a similar statement in the movie Melancholia, though that did not work out too well).  Even in the worst case scenario we are not looking at a 6-mile wide asteroid like the one that hit 66 million years ago (the effect of which is being questioned), but this is quite an event.  The closest the asteroid should get will be about 17,200 miles above the Earth's surface, or about one-tenth the distance between Earth and moon.  To date, the only Earth objects threatened by this large rock would be some of the weather and communications satellites circling the Earth.  The International Space Station orbits well below the expected path of 2012 DA14 at an altitude of 240 miles.  You can see some of the risk calculations in the box below from NASA (good luck). 

NASA noted that this asteroid was only discovered recently: 

2012 DA14 has not been in our catalogs for very long -- it was discovered in February 2012 by astronomers at the La Sagra Sky Survey program in southern Spain and reported to the Minor Planet Center. The asteroid had just made a fairly distant passage by the Earth, about 7 times farther than the distance to the Moon when it was first detected by the Spanish group. Since 2012 DA14's orbital period around the Sun has been about 368 days, which is very similar to the Earth's, the asteroid made a series of annual close approaches, this year's being the closest. But this encounter will shorten 2012 DA14's orbital period to about 317 days, changing its orbital class from Apollo to Aten, and its future close approaches will follow a different pattern. The close approach this year is the closest the asteroid will come for at least 3 decades. 

This passage of 2012 DA14 by the Earth is a record close approach for a known object of this size. A few other known asteroids have flown by the Earth even closer, but those asteroids were smaller. On average, we expect an object of this size to get this close to the Earth about once every 40 years. An actual Earth collision by an object of this size would be expected much less frequently, about once every 1200 years on average. 

This all sounds very reassuring, until you also read:
 
Scientists believe there are approximately 500,000 near-Earth asteroids the size of 2012 DA14. Of those, less than one percent have been discovered...

Asteroid 2012 DA14 will not impact Earth, but if another asteroid of a size similar to that of 2012 DA14 (about 150 feet across) were to impact Earth, it would release approximately 2.5 megatons of energy in the atmosphere and would be expected to cause regional devastation.

A comparison to the impact potential of an asteroid the size of 2012 DA14 could be made to the impact of a near-Earth object that occurred in 1908 in Tuguska, Siberia. Known in the asteroid community as the "Tunguska Event," this impact of an asteroid just slightly smaller than 2012 DA14 (approximately 100 – 130 feet/30-40 meters across) is believed to have flattened about 750 square miles (1,200 square kilometers) of forest in and around the Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Russia. 

Good grief! Do you feel better now?

Update:  All is well.  2012 DA14 safely passed by Earth with no damage to those below. NASA provided the image below from the telescope known as the iTelescope.net Siding Spring Observatory in Australia.