Robot explorers observed a comet as it whizzed past Mars, there's something very odd about a moon of Saturn, and Earth's magnetic field will probably flip much sooner than predicted.About Earth's magnetic poles switching places: I'm pretty sure we'll notice the event, but it won't be 'apocalyptic.'
- Racing Past Mars, Heading Sunward
- Wonky or Awash: Mimas, Moon of Saturn
- Magnetic Flip: Here We Go Again
"Beware the Ides of March;" "Hail, Macbeth;" and All That
I enjoy drama with mildly-melodramatic portents and omens, like the soothsayer's "beware the ides of March;" and the "boil, boil, toil and trouble" threesome's oddly specific remark about who couldn't kill Macbeth.More specifically, I enjoy that sort of thing in plays, movies, and stories.
News with headlines like this? Not so much.
"Earth's magnetic field 'could flip in the space of 100 years', scientists warn"Happily, not all news about the impending magnetic field flip lead with reminders of the "Mayan apocalypse." I've written about doomsday predictions before:
(Rob Waugh, Metro.co.uk (October 21, 2014)
"...Earth's magnetic field can flip far faster than previously thought – unleashing a force which Mayan apocalypse believers thought might destroy our planet in 2012...."
- "Human Folly and Body Counts"
(February 25, 2014)
Particularly - "Apocalypse Whenever"
(June 14, 2011)
Geomagnetic Reversal: Been There, Done That
(From NASA, via Wikimedia Commons, used w/o permission.)
("NASA computer simulation using the model of Glatzmaier and Roberts. The tubes represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical. The dense clusters of lines are within the Earth's core."
(Wikipedia))
Earth's magnetic field is weakening a whole lot faster than scientists expected. Our planet's north and south magnetic poles will switch places "soon:" on the geologic time scale.
More-or-less-breathless journalism notwithstanding, magnetic poles switching places isn't anything new. Geomagnetic reversal generally happens every 100,000 to 1,000,000 years. ("Geomagnetic Reversals: Rates, Timescales, Preferred Paths, Statistical Models and Simulations," Catherine Constable, Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography (September 30, 2001))
Sometimes the magnetic poles stay put for much longer, sometimes they're downright twitchy. The Laschamp event, 41,400 years back — give or take a couple thousand years — lasted centuries, not millennia.
That time, the temporarily-reversed field was was 75% weaker than today's norm: and the strength dropped to only 5% of the today's value during transition. We know there was more radiation reaching Earth's surface then, since scientists found beryllium 10 in a Greenland glacier.
But humans didn't have newspapers and the evening news then: and I'm getting ahead of myself.
Evidence and a Cosmic Coffee Cup
I explained why I think Earth is more than 6,018 years old two weeks ago, and why I'm sure Earth isn't flat the week before that. (October 10, 2014; October 3, 2014)
As a Catholic, I have to take the Bible, Sacred Scripture, very seriously. It's in the rules. (Catechism of the Catholic Church, 101-133)
But I'm not obliged to assume that the Bible is a science textbook: or written from the viewpoint of a metaphor-challenged contemporary American.
Since I'm a Catholic, I must believe that God created, and is creating, a good and ordered physical world: a universe that's changing, in a state of journeying toward an ultimate perfection. (Catechism of the Catholic Church, 282-308)
I must also believe that God is infinite and eternal, almighty and ineffable: beyond our power to describe or understand. (Catechism, 202, 230)
If God had wanted to create a universe where Earth was a doughnut suspended over a cosmic coffee cup: that's the way it would be. But evidence very strongly suggests that this is not the case.
Moving on.
1. Racing Past Mars, Heading Sunward
(From Damian Peach, via BBC News, used w/o permission.)
("Astrophotographer Damian Peach captures Siding Spring (green smudge at lower-centre) on approach to Mars (saturated star-like object)"
(BBC News))
"Comet Siding Spring skims past Mars"I read stories about "outposts at Mars" in my youth. Back then, most science fiction writers assumed that the outposts would house human beings: perhaps with a robot servant to add a bit of excitement.
BBC News (October 19, 2014)
"A recently discovered comet has whizzed past Mars, giving scientists a unique chance to study an object from the farthest reaches of the Solar System....
"The comet, known as Siding Spring, raced past Mars at 56km per second (125,000mph), missing it by 139,500 km.
"Rovers on the Martian surface and satellites were primed to catch the event on their cameras and instruments.
"Siding Spring comes from the Oort Cloud - a spherical region of space far beyond the planets....
"...'Siding Spring probably got knocked into the inner Solar System by the passage of a star near the Oort Cloud,' said Carey Lisse, from the Johns Hopkins University Applied Physics Laboratory, US.
" 'So think about a comet that started to travel probably at the dawn of man and it's just now coming in.
" 'And the reason we can actually observe it is because we've built satellites and rovers and we've now got these outposts at Mars. That's pretty exciting.'..."
That was then, this is now. Humans have walked on Earth's moon, but the vast bulk of exploration has been done by robots: including those Martian outposts.
Enough reminiscing.
The second image, from Nick Howes and others, shows Comet Siding Spring below and to the right of Mars. The comet's official name is C/2013 A1.
"C/2013 A1" is a tad awkward to remember, though, so astronomers call it Siding Spring. That's because Robert McNaught, who spotted it in January 2013, was at Siding Spring Observatory near Coonabarabran, New South Wales, Australia.
Siding Spring's nucleus is small: roughly a kilometer, 3,300 feet, across. Those pictures show gas boiling off the nucleus as sunlight heats it, and dust that was embedded in the frozen gas.
Two astronomers, Estonian Ernst Öpik (1932) and Dutch Jan Oort (1950), said that long-period comets probably came from an orbiting cloud far beyond the known planets.Since then, astronomers have worked out what shape the "Oort cloud" is, based on orbits of comets that take more that 200 years to circle our Sun.
It's still unexplored territory, though. Our knowledge of it comes from studying comets, after they drop into our part of the Solar System.
The Oort could seems to be debris left over from the Solar System's formation some 4,568,000,000 years back. Comets like Siding Spring are opportunities to learn more about that era: and our only chance to get samples, until we send probes into the Solar System's borderlands.
A Robot's Report from Mars
"Mars Reconnaissance Orbiter Mission Status Report"Mars Reconnaissance Orbiter and other satellites were getting data about the Martian atmosphere, too. Scientists expect measurable heating, and maybe changes in Martian winds.
JPL/NASA press release (October 19, 2014)
"NASA's Mars Reconnaissance Orbiter, which has sent home more data about Mars than all other missions combined, is also now providing data about a comet that buzzed The Red Planet today (Oct. 19)....
"...Following the critical period of dust flux, the orbiter is communicating at 1.5 megabits per second with NASA's Deep Space Network. It remained on Side A of its two redundant computers, and all subsystems are working as expected.
"Downlink of data has begun from today's comet observations by three instruments on Mars Reconnaissance Orbiter. The full downlink may take days....
"...Objectives of the observing program are to attempt to image the comet nucleus, to study its surrounding coma of dust and gas, and to search for signatures of that material interacting with the Mars atmosphere. Observations of the comet will continue for another day or so, as the comet and Mars separate, with the comet reaching its closest approach to the sun in about a week, on Oct. 25...."
That's "measurable," not "catastrophic."
Folks have been edgy about comets long before we learned that they're not a weird sort of weather.That illustration shows the impending destruction of Earth by a comet on June 13, 1857. The comet didn't show up.
Hally's Comet did swing by Earth in 1910, though. Our planet passed through the comet's tail: with the usual results:
"...The 1910 pass of Earth was especially close and, thanks to expansive newspaper coverage, eagerly anticipated by the general public. In fact, Earth's orbit carried it through the end of the comet's 24-million-mile-long tail for six hours on May 19, earning the story the day's banner headline in The New York Times.
"While most reporters of the day turned to astronomers to get the facts straight, the yellow press chose to pursue the story in more fanciful ways, helping to fuel the fears of the impressionable that the end of the world was nigh. Despite some published reports leading up to the event, the comet's tail did not contain poisonous gases, and there was never any danger of a celestial collision, either...."
("May 19, 1910: Halley's Comet Brushes Earth With Its Tail," By Tony Long, Wired (May 19, 2009))
Today's "yellow press" is the sort of "FBI CAPTURES BAT CHILD!" thing you'll see in supermarket checkouts: and it's as fanciful as ever. My opinion.The old "shocking secrets revealed" schtick is still going strong, and so is an — imaginative? — approach to science.
Getting back to Comet Siding Spring, the NASA/JPL press release says that one of their goals is learning more about the Solar System's early days.
Eventually, I'm pretty sure we'll have probes exploring the Oort cloud, getting samples before they fall toward the sun. Meanwhile, I'm looking forward to seeing what scientists learn from Comet Siding Spring: after the download's done.
The next upgrade in long-distance service between Earth and Mars may include significantly faster service, and that's another topic. (August 1, 2014)
2. Wonky or Awash: Mimas, Moon of Saturn
(From , NASA/JPL, via BBC News, used w/o permission.)
("The enormous Herschel Crater makes Mimas look rather like the Death Star space station from Star Wars"
(BBC News))
"Death Star moon may be 'wonky or watery' "
Jonathan Webb, BBC News (October 16, 2014)
"The internal structure of one of Saturn's moons is either wonky or awash with water, according to a new study.
"Mimas is nicknamed the Death Star because it resembles the infamous Star Wars space station.
"It has a tell-tale wobble that is twice as big as expected for a moon with a regular, solid structure.
"The researchers offer two explanations: either it has a vast ocean beneath its surface, or a rocky core with a weird shape resembling a rugby ball...."
I'm an American, and none too obsessed with sports, so I needed to look up "rugby ball," to see what one was shaped like.If Jonathan Webb had simply written "prolate spheroid," I'd have known exactly what he meant.
I think he made the right choice, though. Most folks reading his article probably know what a rugby ball looks like.
Moons of the Outer Planets
Until the last decades of the 20th century, we didn't know much about moons of Jupiter, Saturn, and the other outer planets.Astronomers could tell how far from their planet the moons were, had a pretty good idea of how big they were, and could make educated guesses about what they were made of: but that was about it.
Scientists were limited to facts, and what they could extrapolate from those facts. Writers and artists could stay 'in the box,' or let their imaginations off the leash: which they frequently did.
Then we started sending robot spaceships to the outer Solar System.
Some moons looked a bit like ours, crater-covered desolate spheres. Others are — different.
Hidden Oceans
We'd known that Saturn's moon Titan had an atmosphere since 1903. The Cassini-Huygens mission gave us maps of Titan's surface. Its lander sent back pictures of pale hills and dark streams.
But Titan is so cold that water is a mineral. Flowing hydrocarbons fill the moon's lakes and rivers.
Saturn's moon Enceladus, and Jupiter's Europa and Ganymede are another matter.Scientists found strong evidence of liquid water on these moons. More accurately, in the moons.
Europa's subterranean (subeuropan??) ocean may have more than twice as much liquid water as Earth's ocean.
Liquid water doesn't necessarily mean life: but it's getting increasingly difficult to rule out that possibility.
I've wondered if the apparently-complex chemistry and layering of Ganymede's ocean might be near the top of possible homes for life on another world.
If we find life that started on another world, I'm pretty sure that it won't be quite like anything we've imagined. And that's yet another topic. (July 18, 2014; May 9, 2014)
Mimas Moves
"Libration" is what astronomers call the sort of wobbling Mimas does. It's a sort of rocking motion. This animation, given to Wikimedia Commons by Tomruen, shows Earth's moon librating during one orbit.Mimas moves more than our moon. A point on its surface moves back and forth by as much as six kilometers: a sizable fraction of the moon's 396 kilometer diameter.
By measuring Mimas's motions, scientists can learn what sort of material is under its surface:
"...'Nature is essentially allowing us to do the same thing that a child does when she shakes a wrapped gift in hopes of figuring out what's hidden inside,' Dr Tajeddine said.Cornell's Dr. Radwan Tajeddine thinks a subterranean (submimantean ??) sea is the most likely explanation for Mimas's wobble.
His team settled on two likely plot twists, wrapped beneath Mimas's icy crust.
Firstly, their calculations suggested that the wobbles could arise from a core that was squashed or elongated by 20-60km: a huge, central rugby ball of rock.
Alternatively, the moon could have a normal spherical core and crust, but separated by a 'global ocean'. That way, Dr Tajeddine explained, 'the shell can wobble more easily, because it's not attached to another mass'...."
(Jonathan Webb, BBC News)
Now that there are at least two plausible explanations for its unusual wobble, scientists will be collecting data to see which one the evidence favors.
Oxford astrophysicist Chris Lintott pointed out what discovering another massive buried ocean could mean:
"...'If the ocean is really there, we're getting to the point where it's just completely standard for icy moons to have substantial bodies of water inside - and that could have interesting implications for how many of these things could support life.' "We may eventually learn that Earth is a strange world: with its ocean on the outside.
(Jonathan Webb, BBC News (October 16, 2014))
3. Magnetic Flip: Here We Go Again
(From UC Berkeley, used w/o permission.)
("...This map shows how, starting about 789,000 years ago, the north pole wandered around Antarctica for several thousand years before flipping 786,000 years ago to the orientation we know today, with the pole somewhere in the Arctic."
(UC Berkeley))
"Earth's magnetic field could flip within a human lifetime"Very few of us live more than a hundred years, so it's easy to think of things like mountains and constellations as permanent fixtures.
Robert Sanders, Media Relations, UC Berkeley News Center (October 14, 2014)
"Imagine the world waking up one morning to discover that all compasses pointed south instead of north.
"It's not as bizarre as it sounds. Earth's magnetic field has flipped – though not overnight – many times throughout the planet's history. Its dipole magnetic field, like that of a bar magnet, remains about the same intensity for thousands to millions of years, but for incompletely known reasons it occasionally weakens and, presumably over a few thousand years, reverses direction.
"Now, a new study by a team of scientists from Italy, France, Columbia University and the University of California, Berkeley, demonstrates that the last magnetic reversal 786,000 years ago actually happened very quickly, in less than 100 years – roughly a human lifetime...."
At the moment, for example, Earth's north pole – rotational pole, not the magnetic one – points at the star Polaris, more or less. We started calling that star "Polaris" about half a millennia back, and as far as one of us is concerned, it's "constant as the northern star." ("Julius Caesar;" Act III, Scene 1; Shakespeare)
But that's changing. About two millennia back, natural philosophers noticed that the autumnal equinox was moving across the sky. There's still debate over whether Aristarchus of Samos or Hipparchus uncovered that phenomenon first, or someone else, and that's yet again another topic.Since then, we've learned that Earth's north pole moves like a wobbling top. Astronomers call that movement axial precession. It takes Earth's axis about 26,000 years to precess all the way around.
Polaris was the north star in Shakespeare's day. "Constant as the northern star" still makes sense, since only about four centuries have elapsed since Shakespeare's day.
Back when Julius Caesar lived, there wasn't a bright 'pole star.' Earth's north pole pointed at a spot between Polaris and Thuban. On top of that, Polaris is a variable star: the closest Cepheid variable:
- "Mysteries of the North Star"
Govert Schilling, Sky and Telescope (June 1, 2004)
"Mutation," "Cancer," and Media Relations
Scientists knew that Earth's magnetic field has flipped many times: but generally assumed that the turnover was a comparatively gradual process. Now there's evidence that the last flip happened "fast," over the course of a century.
That's the "science" in the article. Now, a few words about emotions and marketing.
Mr. Sanders uses emotionally-charged words like "mutation" and "cancer." I don't blame him. UC Berkeley Media Relations pays him, so he's obligated to make this bit of science news as juicy as possible.
My guess is that one of UC Berkeley Media Relations priorities is getting UC Berkeley's name into as many news services as possible.
Since readers of England's Daily Star and Daily Mirror, and America's The Globe and The National Enquirer, probably get more excited about "mutation" and "cancer" than the Brunhes–Matuyama reversal, Mr. Sanders' rhetoric makes sense. From a marketing point of view.
To his credit, he also pointed out that Earth's magnetic field flips are routine; and don't seem to have had much effect on terrestrial life:
J. Jonah Jameson and the Geologic Time Scale
I agree: Earth's next magnetic field reversal could "potentially wreak havoc," with emphasis on "potentially." That's assuming that we do nothing while it's happening: aside from sitting around, worrying."...The discovery comes as new evidence indicates that the intensity of Earth's magnetic field is decreasing 10 times faster than normal, leading some geophysicists to predict a reversal within a few thousand years.
"Though a magnetic reversal is a major planet-wide event driven by convection in Earth's iron core, there are no documented catastrophes associated with past reversals, despite much searching in the geologic and biologic record. Today, however, such a reversal could potentially wreak havoc with our electrical grid, generating currents that might take it down...."
(Robert Sanders, Media Relations, UC Berkeley News Center)
News media has picked up the "within a human lifetime" angle and run with it. But since I don't work for a real-world equivalent of J. Jonah Jameson, I can point out that Earth's next magnetic field reversal is just around the corner: on the geologic time scale.
On the human time scale "a reversal within a few thousand years" isn't exactly immediate.
Putting "A Few Thousand Years" in Perspective
Let's imagine a hypothetical situation, where natural philosophers realized that Earth's magnetic field would turn around in a few thousand years — during the reign of Enlil-nadin-ahi, last Kassite king of Babylon. That was about 3,170 years ago: so I could say it's "a few thousand years" back. Shortly after becoming king, Enlil-nadin-ahi lost a war: which finished the Kassite dynasty.
Over the next century or so, civilization as Enlil-nadin-ahi knew it ended. We don't know exactly what happened. Some events of the crisis may have been woven into tales of the Trojan War: generations after the collapse.
Time passed. Greek philosophers discussed life, the universe, and everything. Romans built roads. Then Western civilization hit another rough patch, roughly 15 centuries back.
About 800 years ago, we started building cathedrals, weren't wiped out by the Black Death, and that brings me up to the present.
Remember those hypothetical natural philosophers and the Kassite king? It's now been "a few thousand years" since they lived.
If we'd had that sort of heads-up on Earth's impending magnetic field reversal — I think we'd have had time and opportunity to cobble together a few contingency plans. I think we'd be ready, even with a mere 2,000 years lead time.
Flip-Flop Fields and Seafloor Stripes
It's been about a hundred years since geologists noticed that some volcanic rocks were magnetized 'in reverse,' as if Earth's north magnetic pole had been where the southern one is now.Scientists started making detailed maps of Earth's magnetic field in the 1950s and 1960s. That's when they discovered very regular magnetic strips on ocean floors.
Occam's razor suggested a simple explanation for those magnetic zebra stripes: seafloor spreading. Actually, it was two other chaps, Frederick Vine and Drummond Matthews, who pointed out the seafloor spreading connection..
William of Ockham was a Franciscan friar who lived in England, about seven centuries back. One his major contributions was the principle of parsimony that's named after him, and that's still another topic.
Seafloor stripes, coupled with radiometric dating, give scientists information about Earth's magnetic field over the last 200,000,000 years: give or take ten million or so.
Any seafloor older than that has been resorbed back into Earth's interior, and I've talked about plate tectonics before. (October 10, 2014; September 19, 2014)
Field reversals get recorded in "frozen" ferrimagnetic minerals on land, too. Scientists have tracked Earth's magnetic field reversals at least as far back as the Kiaman reversal: 262,000,000 to 318,000,000 years ago.
Scientists thought that mass extinctions might be caused by these magnetic flips.
Someone worked out a worst-case scenario where Earth's magnetic field disappeared entirely, and stayed that way. If that happened, the idea was that Earth's atmosphere would get blown away by the solar wind and Earth would end up looking like Mars.
Magnetic flip-flops have been happening for at least a third of a billion years, and we're still here. Scientists found statistically significant increases of beryllium-10 deep in Greenland's ice sheet: but so far, it looks like Earth's biosphere stays in good working order, no matter where the magnetic poles are.
That's reality. And now, the news.
"...On the Brink..." — Scary Headline, Quiet Disclaimer
(From Getty images, via Express; used w/o permission.)
("The Earth's magnetic field could flip, warn scientists"
(Express))
"North and South flip: Earth's magnetic field may be on brink of switching, warn scientists"This article's headline and lead paragraphs have plenty of emotionally-laden phrases to get the reader's attention: "on brink," "warn," and "alerted governments to a possible world blackout."
Levi Winchester, Express (October 11, 2014)
"EARTH could be on the brink of a magnetic flip - causing what we know as north and south to turn upside down and switch, according to scientists.
"Our planet's magnetic poles have flipped before - with the last time being 780,000 years ago, say geophysicists.
"But now it looks as though our magnetic field is set to switch again and according to new research, it could happen sooner than first thought.
"Scientists have warned this could affect power grids and communication devices across the world. Experts are even said to have alerted governments to a possible world blackout as a result.
"The earth's magnetic field is weakening ten times faster then previously believed - decreasing in strength by about five per cent a decade rather than five per cent a century.
"This weakening field indicates an impending flip in poles, with scientists estimating that this process could begin in less than 2,000 years...."
That's why I make a habit of reading past the lead material and thinking, if I see something interesting in the news.
Credit where credit is due: Mr. Winchester does say that the next flip could begin "in less than 2,000 years."
Even better: his article quotes a scientist, giving Gary [A.] Glatzmaier's name, and where the quote comes from:
- "Earth's Impending Magnetic Flip"
A geomagnetic reversal may happen sooner than expected
Annie Sneed, Scientific American (September 16, 2014)
"...Mr Glatzmaier himself acknowledges that there have been several false starts throughout history - adding that the field would need to weaken at its current rate for around 2,000 years before the process begins...."Like I said before, with that much time to prepare: I think we can deal with the situation when it comes.
(Levi Winchester, Express)
stuff:
- "Caesar, Civilization, Dealing With Change — and Building a Better World"
(August 31, 2014)
Particularly - "Kapteyn b, Habitable Zones, and Using Our Brains"
(July 18, 2014)
Particularly - "Habitable Worlds, Homer, and Haldane — or — Ganymede's Oceans, and Imagining Kepler-186f's Sunsets"
(May 9, 2014)
Particularly - "Scorpions, Acid Rain, and the Great Dying"
(November 29, 2013)
Particularly - "Life in the Universe, God, and Getting a Grip"
(October 17, 2013)
Particularly
- Earth's magnetic poles
- "Earth's Impending Magnetic Flip"
A geomagnetic reversal may happen sooner than expected
Annie Sneed, Scientific American (September 16, 2014) - The Kiaman Reversed Polarity Superchron at Kiama: Toward a field strength estimate based on single silicate crystals"
Rory D. Cottrella, John A. Tardunoa, John Roberts; Physics of the Earth and Planetary Interiors, via Science Direct (August 2008) - "Geomagnetic Reversals: Rates, Timescales, Preferred Paths, Statistical Models and Simulations"
Catherine Constable, Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography (September 30, 2001))
(From igpphome.ucsd.edu/~cathy/Publications/Preprints/geomag_reversals_preprint.pdf (October 22, 2014)) - Wikipedia
- "Earth's Impending Magnetic Flip"
- Mimas
- Herschel (Mimantean_crater)
Wikipedia - Mimas (moon)
Wikipedia - "Wobbling of a Saturn moon hints at what lies beneath"
Blaine Friedlander, Cornell Chronicle (October 16, 2014)
- Herschel (Mimantean_crater)
- Comet Siding Spring and the Oort cloud
- Comet Siding Spring
Near Miss with Mars!
NASA (October 19, 2014
- Comet Siding Spring
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