Category Archives: Solar System

Articles about our Solar System

Voyagers to the Stars

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Voyager: One who takes a long and sometimes dangerous journey involving travel by sea…or in space.

Forty years ago two intrepid spacecraft, aptly named Voyager 1 and 2, set off on a remarkable journey dubbed the “Grand Tour” to visit the gas giants in the outer solar system. Launching Voyager 2 on August 2 and Voyager 1 on September 5, 1977, NASA took advantage of an alignment of the outer planets that made it possible (economically and energy-wise) to visit at least Jupiter and Saturn and potentially Uranus and Neptune. This alignment wouldn’t occur again for 176 years.

Voyager (Image courtesy of NASA)


Although Voyager 1 launched after Voyager 2 it took a faster path and arrived at Jupiter ahead of Voyager 2. Voyager 1 flew by Jupiter and used the gas giant’s gravity to boost its speed and change direction to head off toward Saturn, retracing Pioneer 11’s journey to Jupiter and Saturn earlier in the decade. The trajectory Voyager 1 had as it approached the ringed giant dictated that it was destined to head out of the solar system above (or north of) the ecliptic, the imaginary plane in which the planets orbit the sun.

NASA had to make a decision with regard to Voyager 2: If Voyager 1 did not successfully complete its pass by Saturn, gathering data on the planet’s largest moon, Titan, Voyager 2’s trajectory would be adjusted to make up for its twin’s shortcomings, otherwise it would encounter the ringed planet and slingshot out to Uranus. To all our benefit, Voyager 1 completed its mission and Voyager 2 went on to visit the ice giants, Uranus and Neptune.

Uranus as seen by Voyager 2. (Image courtesy of NASA/JPL)

Neptune as seen by Voyager 2 (Image courtesy of NASA/JPL)

The probe was not designed from the start to encounter the last two distant planets, but it was designed to be reprogrammed on the fly. So NASA engineers rewrote Voyager 2’s programming to account for the much lower light levels at these greater distances from the sun, allowing the probe to capture the first closeup images of Uranus and Neptune. In 1989, after its encounter with Neptune, Voyager 2 took a southerly path below the ecliptic plane and off toward interstellar space.

Today, both probes are still transmitting data from a half dozen or so instruments, their optical cameras and infrared sensors have long since been shut down to conserve power. Notably, Voyager 1 has passed the boundary between the sun’s influence in our solar system and interstellar space known as the heliopause. We find Voyager 1, the most distant object man has ever sent into space, moving beyond 21 billion kilometers (12.9 billion miles) moving at a speed of 61,000 kph (38,000 mph). It takes almost 19.5 hours for a data transmission to reach Earth from Voyager 1 moving at the speed of light. Voyager 2 is a bit closer at 17 billion kilometers (10.5 billion miles) and is moving slower at about 56,500 kph (35,000 mph) with a transmission time of almost 16 hours.

The radio that the probes carry only transmits at 23 watts. That’s about 5 times a typical cell phone’s transmission power we carry around with us. Since the strength of the signal is reduced by the square of the transmission distance, the signal that we receive from Voyager 1 is really, really small: a tenth of a billionth of a trillionth of a watt. That’s .0000000000000000000001 watts. A very small number! To try to put this is some sort of perspective (and even this is hard to grasp!):

If you dropped a grain of salt from the tabletop to the floor, the energy contained in that grain of salt is 10 x 1 million x 1 billion times larger than the energy contained in Voyager’s signal for one second!

As amazing as it is that these spacecraft have been in space for 40 years and are at these extreme distance, to me, it’s even more amazing that we can detect these signals. We use a network of radio telescopes called the Deep Space Network (DSN) that are superbly designed to pick up these astonishingly small signals. There are three sites across the globe that contain multiple radio telescopes to maintain communication with the distant probes in space. The are located in Canberra Australia, Madrid, Spain and Barstow, California (Goldstone). The facility in Canberra is the only site that has a view of Voyager 2 as it exits the solar system to the south, consequently Canberra had to have its antenna dish increased in diameter in 1987 from 64 meters to 70 meters to be able to track Voyager 2’s diminishing signal.

Radio Telescope, Canberra Au. (Image courtesy of NASA)

The Voyagers will eventually stop transmitting around 2030 as their radioisotope thermoelectric generators (RTGs) finally are depleted. The probes will continue on their respective journeys unimpeded. They will not slow down and will not change direction unless something, or someone interferes with them. They may survive for tens of millions of years – a calling card with a Golden Record carrying representations of the inhabitants from a nondescript little water-planet orbiting a very run-of-the-mill star in an arm of the Milky Way Galaxy.

References:

  1. Check on the latest status of Voyager 1 and 2: https://voyager.jpl.nasa.gov/mission/status/
  2. Indepth review of Voyager 2’s mission: https://solarsystem.nasa.gov/missions/voyager2/indepth
  3. A nice review of the Voyager missions: https://theconversation.com/from-the-edge-of-the-solar-system-voyager-probes-are-still-talking-to-australia-after-40-years-82512
  4. https://voyager.jpl.nasa.gov/mission/science/thirty-year-plan/

Till next time,

RC Davison

Cassini’s Garden

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Wallpaper - Cassini's Garden

Cassini’s Garden

Cassini’s Garden was originally created to commemorate the amazing probe that has been in space for almost 20 years and orbiting Saturn and collecting data since 2004. But, it’s not just the machine, it’s the international group of people that worked together to make the mission happen.

Originally known as Cassini-Huygens, which identifies the Huygens lander that was carried onboard Cassini and successfully touched down on Saturn’s largest moon, Titan, on January 14, 2005. Huygens was provided by the European Space Agency (ESA) and along with the Italian space agency, Agenzia Spaziale Italiana (ASI) and NASA formed the three partners for the mission. In total there were 17 countries involved in the mission. In all, over five thousand people have touched this mission since its development began in 1990; from engineers, technicians, designers, machinists, scientists, astronomers and a host of other specialists from around the world.

The Cassini mission has exemplified the best of what we can do when we cooperate together; something that is painfully lacking around the world today when it is needed most. The data produced by this mission is available to everyone – everybody on this planet benefits from the international cooperation that gave birth to Cassini-Huygens.

Cassini’s Garden shows a monument to the enduring probe that has been erected on Enceladus sometime in the future when we humans are no longer defined by our differences.

The probe has had a few problems during its tour but nothing that has diminished its mission nor prevented it from being extended two more times after its initial 4 year jaunt. The only thing that has forced Cassini to end its mission now is that it is running out of fuel, and to prevent it from potentially contaminating Titan or Enceladus with microbes from Earth, it will be directed to fly into Saturn on September 15, 2017. Truly a sad day for everyone involved with this noble machine or that have followed its mission over the years.

And, speaking of potential for life, a paper has recently been published discussing the data Cassini has collected from a fly-through of the plums of water ice and gas venting from the small moon Enceladus’ southern pole in October of 2015. This data revealed the presence of molecular hydrogen (H2) in the gas/ice cloud, which was mostly water.  The presence of hydrogen indicates that there may be hydrothermal vents on the ocean floor of Enceladus.  A chemical reaction between the water and the rocks on the ocean floor, driven by the heat could create the hydrogen. This in turn could be used by bacteria as a food source when combined with carbon dioxide dissolved in the water.

The H2 is not direct evidence of life, but compelling evidence that all the right ingredients are there to support life – probably bacterial – like we see around the hydrothermal vents in our oceans. One more feather in Cassini’s cap!  Check out NASA’s website for more information on this.

Cassini’s Finale – Plunging between the inner rings and Saturn’s atmosphere.

With Cassini setting up to dive between the planet and its inner rings later this month as a finale to its mission, we can expect to see some really amazing images and learn more about this majestic ringed planet than ever before. And, as the data is processed and digested we can expect more revelations about this planet in the years to come.

Thank you to the Cassini team for all their hard work and an amazing ride!

For more information check out Cassini’s Grand Finale.

Till next time,

RC Davison

A Comet, a Moon and a Planet – a Tale of Two Tails

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Comet Catalina by Greg Hogan

Sometimes a picture captures just the right moment in space and time and shows us more than the obvious when we take a closer look. The great picture above, taken by Greg Hogan shows the comet Catalina visiting the morning sky with the crescent Moon and blazingly bright planet Venus. Focusing in on the wispy comet just left of center at the bottom of the image, one will notice that it looks more like a clock captured at five minutes before four. This image shows very nicely the two distinct tails that a comet can form as it dives into the inner solar system to swing around the Sun and back out again. The two tails accompanying a comet are distinctly different: one being a dust tail and the other an ion tail.

The coma or cloud around the head or nucleus of a comet, along with its tails start to form out around the orbit of Mars as the comet warms with the increasing amount of energy it’s receiving from the Sun. The comet is composed of ice (frozen gases, and water), dust, dirt and rock and is sometimes referred to as a “dirty snowball”. As it moves closer to the Sun it continues to heat up, and the ices begin to sublime or convert directly to a gas without going through a liquid phase. This release of gas carries dust particles with it, which destabilizes the comet’s surface allowing larger particles to be released, all of which contributes to the coma and tails. Intense jets of gas, can push even more material away from the comet. It is this debris trail that becomes the source for an annual meteor shower if and when the Earth crosses the path of the comet, such as the Perseids we see in the middle of August every year, which is from Comet Swift-Tuttle.

The dust tail reflects the sunlight and appears white in color similar to the coma. The dust is launched from the comet’s surface and slowly moves away from its host. These particles will begin orbiting the Sun on their own trajectory as they escape the gravitational influence of the comet. They are also pushed away from the comet by the radiation pressure from the Sun. This radiation pressure is due to the transfer of momentum from a light particle (photon) to the dust particle when they collide. This is exactly how a solar sail works. The dust tail will flow behind the comet and as the comet rounds the Sun the tail can become curved as the particles of dust are pushed by the light, as can be seen in the image below of comet McNaught.

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Comet McNaught’s dust tail – Image by Robert H. McNaught

The gas particles that are released by the comet will form the ion tail It is typically bluish/greenish in color and occurs because these gas particles liberated from the comet become “ionized” or charged by the high energy ultraviolet light emitted by the Sun. Once the atoms and molecules of gas become charged they will now be influenced by the magnetic field associated with the solar wind that comes from the Sun. The solar wind is a collection of high energy particles that the Sun radiates and entrained with this stream of particles is a magnetic field pointing away from the Sun. So the ion tail will point directly away from the Sun while the dust tail indicates the path the comet has taken. The ion tail can exhibit knots and twists due to the magnetic field as can be seen below.

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Comet Catalina’s twisted ion tail. Image courtesy of CometwatchUK

The  amazing image below shows comet Encke being buffeted by a coronal mass ejection (CME) from the Sun. The comet’s tail detaches as the mass of solar particles sweeps by and then quickly reforms. This is believed to be caused by the magnetic field retained in the CME interacting with the ion tail’s field. The video is from NASA’s STEREO solar mission.

Comet Encke’s interaction with a CME

If you look in Greg’s picture at the Moon you will see that it is illuminated on lower right hand side by the Sun, which is out of frame in the lower right. Now look closely at comet Catalina and at the “minute hand” of the clock – the ion tail; it’s pointing directly away from the Sun, while the “hour hand” – the dust tail is pointing more towards the Sun indicating that the comet is moving away from the Sun and heading back out of the solar system.  Catalina passed closest to the Sun on November 15, 2015 and will be closest to Earth on January 12, 2016.

Comet Catalina will make only a one-time appearance, as it has gained enough energy on its dive through the inner solar system that it will be jettisoned into interstellar space, never to return. On its journey it will pass through two large reservoirs of comets and other leftover debris from the early solar system that orbit our star, the Kuiper Belt and the Oort Cloud.

Comets originating in the Kuiper Belt, about 30 – 55 times the distance the Earth is from the Sun are known as short period comets, and have periods less than 200 years. Halley’s comet is a well known short period comet, having a period of about 76 years. Note that the Kuiper belt starts at the orbit of the planet Neptune. (Yes, Pluto is a Kuiper Belt object!) (The average Earth-Sun distance is 93 million miles or 150 million km and has been established as a standard unit of distance in astronomy known as an Astronomical Unit or “AU”.)

Long period comets originate from a much more distant region of the solar system, the Oort Cloud. This cloud of frozen debris extends from 5,000 AU to 100,000 AU. Way out there! These comets can have periods as long as 30 million years to complete an orbit around the Sun. Comet Catalina most likely originated from here.

Catch a glimpse of comet Catalina if you can in January, as it will be on the edge of naked-eye visibility, so under the right conditions you won’t need binoculars or a telescope, but they will make for much better viewing. Comets are relics of the early solar system and the more we can study them, the more we learn about how our place in space has formed.

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Jets on comet 67P from OSIRIS Imager on Rosetta – Image courtesy of the European Space Agency

Check out the European Space Agency’s site for amazing pictures and details on comet 67P (Churyumov-Gerasimenko) that their probe Rosetta has been flying in formation with for the last year.

Till next time,

RC Davison

References:

http://www.nasa.gov/sites/default/files/145944main_Kuiper.Belt.Lithograph.pdf

https://ase.tufts.edu/cosmos/view_chapter.asp?id=12&page=5

http://astronomy.swin.edu.au/cosmos/C/cometary+dust+tail

http://secchi.nrl.navy.mil/Publications/Vourlidas_encke_07.pdf

 

Asteroid 2004 BL86 Flyby on January 26, 2015 -Watch Out!

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We will have a celestial visitor to our neighborhood on the 26th of January as asteroid 2004 BL86 passes by the Earth at a distance of about 745,000 miles (1.2 million kilometers). This is about three times the distance from the Earth to the Moon, so we don’t have anything to worry about—this time.

Asteroid 2004 BL86 Flyby – Image courtesy of NASA/JPL

But, what if it wasn’t missing us? What if it had a direct bead on Earth? What would we be doing today? Would Putin still be fanning the flames in the Ukraine? Would ISIL still be executing innocent people in their quest of world domination? Unfortunately, I think that the answer to these questions is probably yes – unless there was no doubt about 2004 BL86 landing in their back yard.

So, what would be the consequences of this asteroid hitting Earth?

First off, it’s not moving that fast—relatively speaking—56,520 km/h (35,120 mph), so it’s energy upon impact at about 6000 Megatons of TNT or 300,000 times the yield of the bomb dropped on Hiroshima, Japan (20 Kilotons of TNT). It could be a lot higher. (That’s a scary thought in its own right!)

The crater that would be left would be 4.7 miles (7.6 km) in diameter and have a depth of 1780 feet (544 meters) covering an area of (17.3 sq miles/45 sq km). The size of the crater alone would wipe out any major city on the planet, but the devastation would extend well beyond that from the fireball generated by the impact, high pressure atmospheric shockwave and seismic shock extending out to a distance of almost 60 miles (100 km). We are talking about tens of millions of people that will no longer exist in instant and millions more that will suffer from the after effects. (The numbers used here come from the calculator: Impact Earth.)

Remember, this is a small chunk of rock!

If it hit in the ocean, say a 100 miles (161 km) off a coastline in about 1000 feet of water, the tsunami waves generated could be between 29.2 feet (8.9 meters) and 58.4 feet (17.8 meters) high and would affect other coastlines around the world to a lesser degree. The size of the wave will change depending on where the asteroid hits the ocean relative to its depth and proximity to the coastlines.

The impact of 2004 BL86 wouldn’t end the world by any means, but it could kill many people and have global impact on international businesses and economies for years to come. The money that each country spends today on defense is money that should be spent on defending this planet from an impact that is surely to come sometime in the future—near or far. We are able to identify many of these objects as to the risks they pose to our planet, but we have not put forth a unified effort on preventing an impact should one be found coming our way. That technology is at hand but needs to be developed and refined.

Please note that the purpose of this exercise isn’t to scare people but to point out that Mother Nature has powers at her disposal that make our most formidable weapons pale in comparison, and the battles we fight on this spec of dust in the cosmos are insignificant. We’ve spent way too much time plotting against each other instead of planning a course of action that will benefit us all. Time marches on and we may be just running out of time to put up a good defense.

So, enjoy asteroid 2004 BL86 as it passes by—there will be plenty of media coverage—and be glad it’s not coming to stay permanently!

Till next time,

RC Davison

The Cost of Cassini at Saturn

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On June 30, 2014 NASA and ESA (European Space Agency), celebrated ten years of unprecedented scientific discoveries of the planet Saturn and its moons by the Cassini-Huygens probe.

Saturn by Cassini showing the prominent hexagonal formation at the north pole. 8-18-14 Credit: NASA/JPL-Caltech/Space Science Institute

The probe has returned well over 350,000 images of the ringed system; discovered seven new moons orbiting the planet, successfully landed the Huygens probe on the surface of Saturn’s largest moon, Titan; over four thousand research papers have been written based on Cassini’s findings; “tasted” the water from Enceladus’ geysers and will continue to send back data until 2017 when it will be intentionally flown into Saturn’s atmosphere.

When we look at all that Cassini has delivered, one can ask – is it worth the $3.27 billion dollars the mission has cost? That’s a whole lot of money!

Titan and Rhea, Saturn’s largest two moons. Image credit: NASA/JPL-Caltech/Space Science Institute

But, when you consider that the mission actually started development in 1990, the cost turns out to be about $130.8 million per year over the last 25 years. Still a lot of money. But, the cost per person in the United States is about $0.42 per person per year (based on an average populate of the US from 1990 to 2014).

The $3.27 billion is the total mission cost to date, but the United State’s contribution was actually $2.6 billion, the balance being supplied by ESA and the Italian space agency, so the per person cost for the US is actually more like 33 cents per person. The per person contribution gets even smaller when you divide the cost by the populations of the ESA supporting countries.

Yes, $3.27 billion is a lot of money, but when you look at it from the perspective of real cost over time it’s not even the cost of a pack of gum per person per year! The flip side of this expense is that the mission development and support employed over 5000 people. That is money that went back into the economy; it put food on the table, paid bills, stimulated local businesses and economies, new technology development, advanced our

Saturn’s amazing rings! Image credit: NASA/JPL-Caltech/Space Science Institute

understanding of the Solar System and of the Saturnian system immensely. The most important contribution (albeit the hardest to quantify) was to excite and encourage a new generation of young people to pursue careers in science and technology.  This one item is so very important in today’s competitive world economy. The return-on-investment is still paying off and will so for many years to come.

As a point of reference, the US Defense Department budget for just 1989 was $389 billion dollars!  For 2014 it is $752 billion.  That works out to $2350 per person today!  $3.27 billion over 25 years doesn’t sound quite so big does it?

Saturn back-lit by the Sun with Mars, Venus and Earth. Image credit: -Caltech/SSI

Take a few moments and check out NASA and ESA’s sites for Cassini and take a look at the amazing images that have been sent back by this enduring probe.  After all, you paid for it!

Check out this video for what to expect for the rest of Cassini’s mission at Saturn.

Till next time,

RC Davison

B612 Foundation: Searching for the Asteroid Threat

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The B612 Foundation is an organization founded by Apollo astronaut Rusty Schweickart and Shuttle astronaut Ed Lu to identify asteroids that may be a threat to our planet Earth and develop the technology to prevent an impact. Pronounced: B – 6 – 12, the foundation is named after the planet in the story, THE LITTLE PRINCE, by Antoine de Saint-Exupery.

In ORBITAL MANEUVERS, the asteroid that impacts Earth was a rogue, passing through our solar system and escaping detection by the underfunded systems which were in place to find such objects. Part of the reason for writing the book was to bring to people’s attention the reality that we are not seeing everything that is out there and the consequences of that can be devastating to all life on this planet.

Meteor over Chelyabinsk, Russia. Credit: Nasha Gazeta newspaper

We had a close call on February 15, 2013. While we were watching asteroid 2012 DA14, a 150 foot (45 meter) hunk of rock fly by the Earth, a smaller asteroid (about 60 feet or 20 meters) blazed through the skies over Chelyabinsk, Russia. Fortunately it only injured about 1200 people and caused about $33 million in damages—it could have been a lot worse! What if it exploded at a lower altitude or impacted in a city…or was bigger?

The B612 Foundation looked at data that the military collected from 2000 to 2013 while monitoring for nuclear explosions and found 26 events that ranged in magnitude from 1 to 600 kilotons of TNT. These were not nuclear events but asteroids detonating in the atmosphere around the globe. The atomic bomb that destroyed Hiroshima at the end of World War II was 15 kilotons…the event over Chelyabinsk was about 600 kilotons. The most significant data gathered from this study is that asteroids large enough to destroy a city enter Earth’s atmosphere at a rate 3 to 10 times higher than were previously thought. The impact from a city-killer asteroid potentially can happen every 100 years. It could happen in 99 years; it could happen in the next minute.

This should be unsettling to anyone reading this. And, even more unsettling is the fact that we have technologies that we can use to prevent these impacts—as long as we have enough advanced warning—but this is not being aggressively pursued by the major governments on this planet. There are organizations like B612 with their Sentinel Mission to find and track asteroids and the Planetary Society’s Laser Bees, which will deflect threatening asteroids.

Check out the video and the B612 Foundation and the Planetary Society’s website for more information. If the major governments of the world aren’t interested in addressing this problem seriously, we can at least provide grassroots support to those groups that are taking on this responsibility.

Till next time,

RC Davison

The Majesty of Saturn

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The Cassini spacecraft has been orbiting Saturn since June 30, 2004 and has returned many amazing images of this majestic planet. On July 19, 2013 Cassini took a series of images over a period of more than four hours that resulted in the image you see here. (Click on the picture for a larger image.)

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Saturn as taken by Cassini on July 19, 2013

The planet is back-lit by the Sun and shows off its spectacular ring system in great detail. From the finely etched inner rings to the diaphanous outer “E” ring, which is created by the ice geysers on Saturn’s moon Enceladus. Enceladus can be seen as the bright dot embedded in the ring on the left side of the image. This ring system spans 404,880 miles (651,591 kilometers). Consider that the average distance between the Earth and our Moon is about 239,000 miles (384,000 km), one can see how our system would fit nicely within Saturn’s rings.

This image is even more remarkable because of the other celestial objects that are also present. Our home planet lies to the lower right of Saturn, while Mars and Venus are above and to the left. There are also seven Saturnian moons visible in the picture. Follow this link for a larger annotated image that highlights these objects.

This isn’t the first time Earth has been photographed from Saturn or even further from home. Check out the blog post “The Pale Blue Dot” if you would like to read more.

One last spectacular image of Saturn, which can be seen below was taken on October 10, 2013. Here, Cassini is flying over the top of the planet and the amazing hexagonally shaped weather system is in full view. If you zoom in to the image you can see numerous smaller cyclonic storms and circular weather patterns near the pole. (Click on the picture for a larger image.)

Saturn from above. October 2013. Image Courtesy of NASA/JPL

These are only a few representations of this beautiful planet that can be found at NASA’s JPL website. For a more detailed discussion of how the latest image of Saturn was taken and processed, check out CICLOPS (Cassini Imaging Central Laboratory Operations)  “The Day the Earth Smiled”.

Two last comments:

The amazing success of the mission, and the wealth of knowledge that Cassini has brought to us about this planet makes me wish that NASA had the foresight to launch similar probes to Jupiter, Uranus and Neptune. Imagine the wonders we would have discovered!

Lastly, Carl Sagan tried to put our fragile existence into perspective when he lobbied NASA to take the first image of our planet from the distant reaches of our Solar System – the original “Pale Blue Dot” image in 1990. For me, it’s hard to look at our planet as a few pixels in the vast blackness of the cosmos and not be reminded of the stark reality that this is the only home mankind has had—and will have—for many, many generations to come. We can’t afford to waste it.

Till next time.

RC Davison

Asteroid 2012 DA14, Tunguska Impact, Meteor Crater, and the Russian Meteor of 2013

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(Post updated 2/19/2013 with latest assessment on asteroid from ESA.)

Wow! Two wake up calls for the planet Earth in one day! Maybe it’s about time that the people of planet Earth realize that they are inside the pinball machine that makes up our Solar System. Sooner or later that ball is going to hit us head on. Today we were lucky – twice!

Russian Meteor, February 15, 2013

The spectacular meteor that streaked across Russia’s sky Friday morning has been estimated to be about 56 feet (17 meters) across, weighing in at more than 7000 metric tons and moving at speed around 40,000 mph (64, 373 km/h). It exploded about 9-12 miles (15-20 km) above the surface of the Earth with an equivalent of 500 kilotons of TNT—30 times the energy of the Hiroshima atomic bomb.  The consequent shockwave shattered windows and damage buildings in and around the Russian city, Chelyabinsk, resulting in over 1000 injuries.

This meteor was not related to the flyby later in the day of asteroid 2012 DA14. This asteroid skimmed by the Earth at a distance a little over 17,000 miles (27,400 km). Friday, February 15, 2013 could have turned out a lot different if either of these cosmic messengers had a slight change in course, which in the case of the Russian asteroid, could have detonated lower and over a more populated area or for 2012 DA14, a direct hit instead of a near miss.

We have two good examples of the consequences of an asteroid the size of 2012 DA14 (150 feet, 45 meters, ~130,000 metric tons) hitting the Earth in the Tunguska explosion of 1908 in Siberia (120 feet, 37 meters, ~100,000 metric tons) and the nickel-iron meteor (150 feet, 50 meters, ~270,000 metric tons) responsible for Meteor Crater in Arizona.

Map of Tunguska Impact (Sullivan 1979 and Kridec 1966.)

The Tunguska explosion occurred in the air above Siberia at a height of about 28,000 feet

(8500 meters) and generated the equivalent energy of about 1000 Hiroshima atomic bombs. The result was over 800 square miles of forest destroyed and a shock waves that

were recorded as far as western Europe and registered a magnitude 5 earthquake. As of today, no crater has been found to mark an impact of the remnants of the asteroid, leading some to think it might have been piece of a comet that entered Earth’s atmosphere that day, which is made mostly of ice.

Meteor Crater (AKA Barringer Crater) Arizona – Wikimedia Commons

Contrasting Tunguska is the nickel-iron meteor that did leave a crater in what is now Arizona. About 50,000 years ago this meteor entered the atmosphere at a speed of about 27,000 mph (43,000 km/hr) and fragmented to some degree due to the stresses associated with entry into the atmosphere, but the bulk of it hit the Earth creating a crater that is 4000 feet (1200 meters) in diameter and 570 feet (174 meters) deep. The explosive energy released from the impact has been estimated to be as high as 200 times that of the bomb dropped on Hiroshima.

Impact effects at Meteor Crater – Image courtesy of the Space Imagery Center and/or David A. Kring

We see two very different effects from two similarly sized asteroids.  But, it is the different composition that makes the difference.  The high density nickel-iron meteor survives the descent to the surface, while the less dense, ice-rich meteor fragments due to the high stresses experienced in its passage through thicker layers of the atmosphere. The temperatures experienced by these fragments can reach 45,000 °F (25,000 °C) causing the massive fireball and resulting shockwave and destruction.

We don’t, by any stretch of the imagination have knowledge of every asteroid in the Solar System that poses a potential threat to Earth.  The more we look the more we see, and with regard to near Earth asteroids (NEA), the sooner we find them the better.  It is possibly the only natural disaster we may be able to avert, given enough time.

Till next time,

RC Davison

References:

Russian asteroid impact ESA update and assessment

The Tunguska Impact – 100 Years Later

Damage by Impact — the Case at Meteor Crater, Arizona

Barringer Meteor Crater and Its Environmental Effects

 

Asteroid Flyby and Pricing Change on ORBITAL MANEUVERS

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This coming Friday, February 15, 2013, we will have a flyby of asteroid 2012 DA14. This asteroid is about 45 meters (150 feet) in diameter and is most notable in that it will pass within the orbits of our geosynchronous satellites, which typically orbit about 22,000 miles (about 35,000 km). It will skim past the Earth at an altitude of about 17,000 miles (27,000 km), so there are no concerns about an impact, but it could (very unlikely!) take out a satellite on its way through our neighborhood.

Trajectory of 2012 DA14 (Image courtesy of NASA)

It is interesting, and a bit concerning to note that the object that exploded over Tunguska, Siberia in 1908 is estimated to be about 120 feet (36 m) in diameter! Here’s an excerpt from NASA’s site on the event:

“It is estimated the asteroid entered Earth’s atmosphere traveling at a speed of about 33,500 miles per hour. During its quick plunge, the 220-million-pound space rock heated the air surrounding it to 44,500 degrees Fahrenheit. At 7:17 a.m. (local Siberia time), at a height of about 28,000 feet, the combination of pressure and heat caused the asteroid to fragment and annihilate itself, producing a fireball and releasing energy equivalent to about 185 Hiroshima bombs.”  – NASA Science News

This leveled over 800 square miles (2072 sq km) of tundra! Imagine that destruction over a major metropolitan area today! Although small, relatively speaking, these objects are moving at very high velocities, which translates into very large amounts of energy that can be released when they explode or impact an object.

Fortunately for us, 2012 DA14’s orbit will cause it to just miss us, but it points out the potential for very catastrophic events to occur from objects that are relatively very small. It was by chance that we discovered it when we did, thanks to work by the Planetary Society.

Our surveillance of the asteroid threat has gotten better, but there is still need for improvement and more importantly, a plan of action to deal with an asteroid that will impact the Earth. This needs to be researched, tested and ready before we find that space rock with our name on it. There is work being done on this, but it is not at the level it should be.  We do not know when we might find a potentially lethal asteroid, and we don’t know how much time we will have to deal with it when it is discovered.  We need to be prepared.  The sooner the better!

Speaking of space rocks destined to impact Earth. The book, ORBITAL MANEUVERS discusses some of the consequences of a very large asteroid impacting the Earth and a stranded space shuttle crew’s attempt to survive the aftermath while in orbit. Part of the reason to write the book was to draw attention to this very real threat. To give more people the chance to read the book and get a sense of what is in store for us should a large impact occur, I’ve reduced the price on the book to $8.95 for the paper back, and $.99 for the electronic versions for Kindle and all other digital formats at Smashwords. It is also available on Apple’s ibooks.  Enjoy!

Keep looking up. You never know what you’re going to see!

Till next time,

RC Davison

What Do You See?

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What do you see in this image from Mars? A spaceship? Some sort of structure? Or, possibly a natural formation of some sort?

Mysterious object spotted on Mars

What is this mysterious object spotted on Mars?

Without too much of a stretch of the imagination I think one could be convinced that this is an image of an alien spacecraft.  But, if you haven’t already peeked at the image below, take a look now to see the image above in the context of its actual surroundings.

Sand dunes on the Martian surface - Image courtesy of NASA

These amazingly fluid structures are formed by wind and sand and are known as barchan dunes. They are not unique to Mars but can also be found on Earth as seen below. Here is another amazing photo of barchan dunes taken by George Steinmetz/National Geographic Society. It’s difficult to look at this image and not feel an alien origin to the shapes we see emerging from the sea of sand.

Barchan dunes in the Arabian Peninsula - Image by George Steinmetz / National Geographic Society

Aside from the stark beauty of these images, I wanted to point out how easy it is to manipulate an image to show something or give the reader an impression of something that doesn’t really exist. Without seeing the context from which the “alien spaceship” was taken, it is difficult to assess the authenticity of the image.

The morale: Don’t believe everything you see and hear.  Always keep an open mind with a bit of skepticism, ask questions and investigate!
Till next time,
RC Davison