Comets, Asteroids, and Interstellar Wormholes

The past couple of weeks have seen a number of space-related events including a probe landing on a comet and the opening of a blockbuster sci-fi film.  It's been a welcome escape from the generally disappointing news that's been inundating us for months.

Comet Churyumov–Gerasimenko/67P from Rosetta's camera

The big news in the "real world" was the European Space Agency's (ESA's) successful landing of its refrigerator-sized Philae probe on the comet Churyumov–Gerasimenko/67P.   The landing on November 12 was the first ever on a comet.  It took place after a ten-year journey of 4 billion miles as the culmination of the ESA's Rosetta mission.  The Rosetta spacecraft was launched in March 2004, rendezvoused with the comet on August 6, 2014 and went into orbit around it on September 10.

Philae after separation from the Rosetta spacecraft

The landing was not without drama.  Philae bounced twice before settling on the surface to begin an analysis of the comet's core.  The bouncing could have jeopardized the mission but all the instruments remained operable.  Fifty-seven hours into its expected sixty-four hour data transmission phase it lost power as its solar-powered battery dropped into standby mode.  "The Philae lander on the distant comet 67P has sent another stream of data back to Earth before losing power.  The little probe delivered everything expected from it, just as its failing battery dropped it into standby mode.  Philae is pressed up against a cliff. Deep shadows mean it cannot now get enough light on to its solar panels to recharge its systems." [BBC News, Nov.15]  As ESA Rosetta Mission tweeted: "S'ok Philae, I've got it from here for now. Rest well...". [The New Zealand Herald, Nov. 16]  When ESA scientists were asked the purpose of the $1.6 billion mission, "Get this, they said: by analysing a comet, Philae would probe the primeval material of the Solar System... the ancient water and carbon which may even have seeded Earth with the means to make life.  Comets are treasure chests, said Mark McCaughrean, senior ESA scientific advisor, before he fed us the jaw-dropping idea: 'We could be comet stuff ourselves.' " [AFP (mirrored by Yahoo News) , Nov.17]  On November 18, ESA scientists confirmed that the Philae lander had detected carbon-containing organic molecules on the surface of the comet.
Photos: ESA

A few days before Philae's landing, I had the pleasure of seeing Interstellar and thus contributed my part to the $130 million that the film grossed globally that first weekend.  Interstellar's plot and subplots, its visual effects, and its reliance on cutting edge science make this nearly-three-hour epic one of the best and most scientifically realistic sci-fi movies ever made.

Earth is dying.  A global ecological disaster is causing dust storms and blights and bringing drought and famine. Growing food has become the number one priority of the planet and the story begins with a struggling farm family somewhere in the American Midwest.  The father, Cooper, played by Matthew McConnaughy, is a former engineer and pilot. "Ghostly" signals caused by a gravity anomaly lead Cooper and his precocious daughter to a secret NASA installation.  A wormhole, leading to another star system with potentially habitable planets, has mysteriously appeared near Saturn.  NASA asks Cooper to pilot the ship that will travel through the wormhole - at the risk of never seeing his family again even if the journey is successful.

Wormholes, black holes, relativistic time dilation, and a fifth dimension all play a role in the film. The internet is full of explanations of the science behind the film. Here is a link to a discussion of black holes and wormholes by Neil de Grasse Tyson.  And here is space.com's infographic, "The Science of Interstellar Explained".  For a fuller explanation of the science behind the movie's events and visual effects, Kip Thorne, the science adviser for the film, has written "The Science of Interstellar".

Interstellar reminded me a bit of 2001: A Space Odyssey, another one of my all time favorites. Both films speculate on deep philosophical questions - mankind's destiny (both), the rise of consciousness and mankind's beginnings (2001), causality (Interstellar) - and develop plots based on classic sci-fi themes - "we are not alone" (2001), exploring the unknown (both) and time travel (Interstellar).  In an interview with The Daily Beast, director Christopher Nolan says "In light of the success and weight of [Star Wars], they re-released Kubrick’s 2001: A Space Odyssey and my father took me to see it on one of the biggest screens in London in Leicester Square, and that was also a seminal experience. I was in awe of the scale of it, the escapist possibilities of it, and the sense of adventure and ability to take the audience across the universe. It definitely stuck in the back of my mind that if I were ever given the chance to give an audience of today that experience, I’d have to try and do that." And well you have, Mr. Nolan.  Thank you.
Posters: Paramount Pictures
Related:
This Final 'Interstellar' Trailer Is Epic and Amazing [space.com, Oct. 1]

If ESA's Rosetta mission searches a comet for clues to the physical origin of life on Earth, NASA's OSIRIS-REx mission may help prepare us for one potential doomsday scenario by studying an asteroid.  Asteroid impacts have caused widespread destruction on the planet.  The most famous of these impacts is the one that formed the Chicxulub crater in the Yucatan about 66 million years ago. It caused one of the greatest extinction events ever, wiping out the dinosaurs and making way for the rise of mammals.  One of the best-known recorded impacts in modern times was the Tunguska event, which occurred in Siberia, Russia, in 1908. This incident involved an explosion that was probably caused by an asteroid or comet bursting apart three to six miles above the Earth's surface, felling an estimated 80 million trees over 830 sq mi.  In February 2013, a near Earth asteroid entered the Earth's atmosphere, causing a fireball near Chelyabinsk, Russia.  More than 7000 buildings in six cities were damaged and about 1500 people were injured by the blast - primarily from broken glass from the shock wave.

Artist's conception of OSIRIS-REx in orbit around Bennu (NASA)

NASA will launch a spacecraft to the asteroid Bennu in 2016.  It will arrive at the asteroid and take samples in 2019, returning to Earth in 2023. NASA believes that the asteroid has been little altered over time and is likely to represent a snapshot of our solar system's infancy. The asteroid also is likely rich in carbon, a key element in the organic molecules necessary for life. Besides this glimpse at the early solar system, the composition of the asteroid will give us a better indication of how to divert the asteroid from Earth impact if that becomes necessary.

The target asteroid, Bennu, is a potential Earth impactor with a diameter of nearly half a kilometer. A 2010 study by an Italian team of scientists and mathematicians located a series of eight potential Earth impacts between 2169 and 2199. JPL's current "Sentry Risk Table" estimates an even greater number of  78 potential impacts,   JPL also shows it to have the second highest probability of impact of all near Earth asteroids greater than 50 meters in diameter.  Bennu's probability of striking Earth is 1 in 2700, a greater risk than that of a person dying in a car crash in a given year.  And if Bennu did hit, the energy released would be more than 5,000 megatons, equivalent to 200 of the most powerful nuclear weapons ever made.
Related
"Why you should care about asteroid 101955 Bennu" [Astro Bob blog at areavoices.com, Aug. 2013]


Featured Video
A new trailer unveiled ahead of the special re-release of 2001: A Space Odyssey as part of British Film Institute's sci-fi season [Hollywood Reporter, Oct. 21]

Featured Posts

Our Closest Call - July 29, 2012

Voyager 1 Has Left the Building- September 15, 2013

Our Closest Call

I'm going out on a limb here but I'll predict that the world will not end on December 21, 2012. The Mayan calendar does end on that date but that is about all that does. The hype surrounding the Mayan calendar sold a few books and spawned a few apocalyptic movies. But nothing, literally, is on the horizon that would support the end-of-world premise.  We do not appear to be heading for an extinction event this year.  But through the long history of our planet, there have been at least five extinction events, i.e., periods during which the majority of species are made extinct. Over the past 500 million years, these have occurred an average of once every 100 million years. 

The most famous and most recent, but not the most destructive, of these events occurred 65 million years ago. The asteroid strike in the Yucatan caused the end of the age of the reptiles including the destruction of the dinosaurs. Discovered in the late 1970's, the Chixculub crater measures more than 110 miles in diameter. It is both a reminder of the fragility of life on this planet and of the good fortune of the small mammals that survived and from which humanity eventually evolved.

The most destructive extinction event occurred about 250 million years ago. “The Great Dying” saw 96% of all ocean species and 80% of all land species extinguished. Although we cannot be certain, it appears that this event was likely a combination of events. Possible culprits include a nearby supernova, environmental changes wrought by the formation of a super-continent, the devastating impact of a large asteroid -- or some combination of these.

Bad as these events were, they were not mankind's closest call. That honor goes to the Lake Toba Volcano eruption about 73,000 years ago. Looks pretty peaceful now, doesn't it?

(Photo is from the Wayfaring.Info website.)

Don't be fooled by Lake Toba's current placid appearance. Seventy-three thousand years ago, an eruption here in northern Sumatra in Indonesia led to a ten-year “volcanic winter”. The Toba event is believed to be the most powerful volcano in the last two million years. It spewed out 28 times the debris of the largest historically recorded volcanic eruption at Mount Tambora in 1815. The Mount Tambora eruption led to “The Year Without a Summer” in 1816, so called because of its impact on North American and European weather.

The Toba eruption and the ensuing “volcanic winter” reduced the human population to as low as 1,000 breeding pairs scattered in small pockets across the globe. Had the eruption been stronger, mankind may have been completely wiped out. I wouldn't be here writing this nor would you be there reading it. What species would take our place? Would the Earth have to wait another 2-3 million years before another land mammal evolved to reach the threshold of self-conscious intelligence? Would dolphins or whales evolve to fill the “consciousness” niche? If so, would a water-based intelligence be capable of creating a technological society? Would dinosaurs make a comeback? Would a hive mind eventually achieve higher intelligence? Or would the Earth remain forever devoid of self-conscious intelligent life?

So back to why the world won't end come this December. Looking over the extinction events of the past half billion years, we see that they were due to massive climate shifts or to large changes in ocean levels. These climate and ocean level shifts were caused in turn by several types of large-scale catastrophic events – changing supercontinent tectonics, volcanic eruptions, supernovae, and asteroid/near-Earth-object impacts. 

Supercontinent tectonics shouldn't come into play any time soon - the supercontinent implicated in the “Great Dying” formed some 300,000 years ago and had the land mass of all the existing continents combined.

While it's impossible to predict massive volcanic eruptions, suffice it to say that the Lake Toba eruption was the largest in at least two million years. 

 

As for a supernova (an exploding giant star) wiping out the Earth, if the dying star is close enough and massive enough and has a suitable companion star, there is nothing that could possibly stop it from bringing civilization to an end. The good news is that the most likely nearby star that can cause this devastation is predicted to go into its final death phase in 10,000,000 years.

 

Near-earth objects then are probably the most likely short-term scenario for wide-spread earthly destruction. There are about 1 million asteroids of a kilometer or more diameter and there are 10,000 asteroids of the size that brought down the dinosaurs. Near-Earth objects are already monitored and tracked closely by NASA and others. Contingency plans are being developed for how to deal with any threats. These plans generally involve nudging the asteroid slightly off its collision course. There are a couple of potentially destruction-wreaking NEO's in our future but we have decades to prepare:

• On April 13, 2029, asteroid 2004 MN4 will fly past Earth only 18,600 miles (30,000 km) above the ground. For comparison, geosynchronous satellites orbit at 22,300 miles (36,000 km). This is a 300 meter asteroid and could take out an area the size of Texas if it hit. As of now, though, astrophysicists are saying that it has no chance of hitting the Earth.

• The 460-foot asteroid 2011 AG5 is estimated to have a 1 in 625 chance of hitting the Earth on February 5, 2040. For comparison, the asteroid that flattened the land around the Tungaska River in Siberia in 1908 was 30-60 ft in diameter.

So it doesn't appear that we should fear extinction as a species anytime soon. Of course, we can always destroy ourselves quickly in a nuclear holocaust or slowly with unaddressed global warming. And what a waste that would be.

A Note for Sci-Fi Fans

I love speculative fiction. It deals with the most mind-boggling concepts imaginable in an engaging way. For an interesting read on a universe where dinosaurs are the dominant intelligent species, see Robert Sawyer's Quintaglio Ascension Trilogy (Far Seer, Fossil Hunter, Foreigner) . Orson Scott Card's Ender's Saga (particularly Ender's Game, Speaker for the Dead, Xenocide, and Children of the Mind) provides, among many, many other things, an exploration of the intelligence of a hive mind. Intelligent dolphins appear several times in David Brin's Uplift anf Uplift Storm trilogies, most notably in Startide Rising. Finally, Charles Sheffield's Aftermath shows the havoc resulting after Sol's nearest neighbor, the twin star system at Alpha Centauri, goes supernova.