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]

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