Vesta: Small World, Big Mountain

"Giant Asteroid Vesta Has Mountain Taller Than Anything on Earth"
Space.com (October 3, 2011)

"A NASA spacecraft orbiting the asteroid Vesta is revealing new details about the huge space rock's surface, including a massive mountain that rises taller than Mt. Everest on Earth.

"NASA's Dawn probe has been circling Vesta since mid-July, when it arrived in the asteroid belt that orbits the sun between Mars and Jupiter. So far, Dawn has beamed back surprising views of Vesta that revealed an enormous mountain in the asteroid's southern hemisphere and show that its crater surface is incredibly diverse place.

" 'We are learning many amazing things about Vesta, which we call the smallest terrestrial planet,' Chris Russell, principal investigator of the Dawn mission, said in a statement. 'Like Earth, Mars, Venus and Mercury, Vesta has ancient basaltic lava flows on the surface and a large iron core … The south polar mountain is larger than the big island of Hawaii, the largest mountain on Earth, as measured from the ocean floor. It is almost as high as the highest mountain in the solar system, the shield volcano Olympus Mons on Mars.'..."

The Space.com article has several NASA photos sent back by the Dawn probe: The Lemming thinks they're fascinating, but someone else might wonder what's the big deal with a grayish pockmarked lump of a mini-planet.

What's most intriguing for the Lemming is the possibility that Vesta's southern mountain isn't essentially the biggest lump on a lumpy pile of stuff. If Vest has - or had - some sort of geological process that pushed that mountain up, we'll have more data to drop into planetary geology models. Or whatever that topic's called. "Planetology" sounds awkward: and that's another topic.

Like Venus, Earth, and Mars, Vesta apparently has two major areas. The asteroid's northern hemisphere has more craters than the southern, and seems to be older. Volcanic activity, long ago? Evidence of a really big impact event on Vesta?

The Dawn probe's next stop is Ceres: ETA 2015.

Related posts:

• "Asteroid Misses Earth, Good News; It's Not Unique, Not-So-Good News"
  (June 29, 2011)
• "2008 LC18 - Neptune Trojan Asteroid Discovered"
  (August 13, 2010)
• "Proposed Commission for Planetary Defense: H.R. 5587 Makes Sense"
  (July 20, 2010)
• "Life on Ceres? Could Be"
  (March 5, 2009)
• "Triple Asteroid Found"
  (February 14, 2008)

Gliese 581 System's Habitable Zone: New Numbers

"Alien Planet May Be in Habitable Zone After All"
Mike Wall, Space.com (December 20, 2010)

"The alien planet Gliese 581g has been getting a lot of attention recently as a possibly habitable world, but a case is building for its next-door neighbor as a good candidate for extraterrestrial life, too.

"Gliese 581d, another planet discovered around the star Gliese 581, may well lie in the 'habitable zone' of the star - that just-right distance range that can allow liquid water to exist — new atmospheric-modeling research suggests. The finding follows closely on the heels of a similar study, published earlier this year, that reached the same provisional conclusion. [Tour of the planets around star Gliese 581.]

" 'The fact that two models find conditions for liquid water could exist, that strongly implies that it is possible,' said the new study's lead author, Philip von Paris of the Institute for Planetary Research at the German Aerospace Center in Berlin. 'It doesn't seem impossible to have life there.'

"The Gliese 581 system: Worlds of possibilities

"Gliese 581 is a red dwarf located 20 light-years from Earth, just a stone's throw in the cosmic scheme of things. Astronomers have detected six planets orbiting the star...."

Actually, the number of planets circling Gliese 581 is under debate. Some scientists who didn't discover Gliese 581g say it's not there: and they may be right. Or, not.

The Lemming thinks that, at this point, it's safest to say that there 'about a half-dozen' planets in the Gliese 581 system, and leave it at that.

Mr. Wall discusses what a "habitable zone" is, and how scientists crunched the numbers to determine what the odds are that water and a breathable-by-something atmosphere could exist on one or more of the planets around Gliese 581.

Star Trek's 'class M planets' notwithstanding, places that wouldn't look much like southern California could support life. Like central Minnesota, for example.

There's even a possibility that Earth is about as small as a planet can be, and still maintain a breathable atmosphere. ("Earth May Not Be a 'Class M' Planet" (December 5, 2009)) And that's (almost) another topic.

That year-old post isn't all that far afield, though: the Gliese 581 planets found (so far) are more massive than Earth. But not by much, in some cases.

As for some balmy tropic world inhabited by beautiful space princesses? That's another topic. ("Beautiful Space Princesses, Almost Certainly Not: Flying Whales, Maybe," Drifting at the Edge of Time and Space (December 8, 2009))

Related posts:

• "Gliese 581g: Then Again, Maybe So"
  (October 14, 2010)
• "Gliese 581g? Maybe Not"
  (October 13, 2010)
• "Gliese 581g, Space Aliens, and the Canals of Mars"
  (October 12, 2010)
• "Gliese 581g, Alien Angst, and the Lemming"
  (October 4, 2010)
• "Gliese 581g: Life? Maybe"
  (October 2, 2010)

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More:

• "Posts About the Gliese 581 Planetary System: Including Gliese 581g"
• "A Serious Search for Other Worlds, Life, and - Maybe - Extra-Terrestrial Intelligence"

Space Walnut! The Strange Ridge on Iapetus

"Cracking a Mystery: Space Walnut Created by Moons Crashing "
Mike Wall, Space.com (December 15, 2010)

"A massive ridge nearly encircling Saturn's moon Iapetus is likely the remains of a mini-moon destroyed by Iapetus' gravity long ago, a new study suggests.

"This sub-moon probably formed after a giant object smashed into Iapetus, and the blasted-off pieces coalesced, according to researchers. But over time, Iapetus tore it apart and its bits slammed into the moon along its equator, forming a ridge more than twice as tall as Mount Everest.

" 'Imagine all of these particles coming down horizontally across the equatorial surface at about 400 meters per second, the speed of a rifle bullet,' study co-author William McKinnon of Washington University in St. Louis said in a statement. 'Particles would impact one by one, over and over again on the equatorial line. At first the debris would have made holes to form a groove that eventually filled up.'..."

Iapetus has a special place for the Lemming, since it's where one of the big black monoliths were in A. C. Clarke's novelization of Kubrick's 2001: a Space Odyssey. A 'making of' book that's - somewhere in the Lemming's attic - explained that Kubrick would have used Clarke's locale: but doing so would have meant special effects to make Jupiter, and then adding rings. Even Kubrick had limits, so that part of the movie was set in orbit around Jupiter.

That self-indulgent stroll down memory lane is to explain why, when the Lemming saw that ridge precisely over the equator of Iapetus, 'artifact' came to mind.

Not as a serious idea: more along the lines of 'that would make a good story.'

The Iapetus feature is unique in the Solar system - the part inside the orbits of Pluto/Charon and Neptune, anyway - but the collision that may have caused it isn't.

Not according to current best-fit models about how planets form, anyway. Right now, it looks like Earth's moon and Charon got started after major collisions kicked up moon-size divots. Debris piles, actually.

One of the reasons no other Saturnian moons have features like this ridge is - probably - that the orbit of Iapetus isn't particularly close to other moons. Other satellites didn't have that kind of elbow room.

More at

• "A Serious Search for Other Worlds, Life, and - Maybe - Extra-Terrestrial Intelligence"

Earth, Gold, the Early Solar System, and New Ideas

"Ancient Crashes Blasted Precious Metals Into Earth, Moon and Mars"
Mike Wall, Space.com (December 9, 2010)

"Gigantic collisions on Earth, the moon and Mars 4.5 billion years ago injected precious elements such as gold and platinum into the developing worlds, a new study suggests.

"In the last days of planet formation, a body as big as Pluto likely slammed into Earth after the planet had been clobbered by a Mars-size object, researchers said. Mars and the moon absorbed smaller but still devastating blows, they added.

"These traumatic cosmic crashes may have knocked Earth off its axis by 10 degrees. But they also delivered gold and other elements into the bodies' upper reaches, and possibly brought huge amounts of water to the moon, researchers said...."

The point at issue is that there's quite a lot of Gold, platinum, palladium, and other elements at and near Earth's surface.

Which shouldn't be there. Assuming that current models for how planets formed are fairly close to being accurate.

The models could be wrong - but there's a whole lot of other data that supports them.

The Space.com article runs through a newish explanation for why thar's gold in that there crust on Earth - which is involved with an explanation for the size range of asteroids is skewed toward big bits of stuff. And the Borealis Basin on Mars. Assuming that it's an impact feature. Which isn't certain.

That lack of certainty will probably be the norm for a while, particularly since we're starting to get data about other planetary systems.

"...The study paints a violent picture of the solar system's early days, with the inner planets being walloped heartily shortly after their birth. Such pummelings might be common in other newly forming solar systems, according to Bottke.

" 'Because we can reproduce some of these things in our models, I think that probably means we're fairly typical,' he said. 'But that's just a guess.'

"If our solar system is atypical — if young planets in other solar systems were spared pummelings by massive impactors late in the formation process — then alien planets might be different in significant ways, Bottke said. Their mantles, for example, might be lacking in siderophiles like gold and platinum, which we value for a variety of reasons.

"In any event, Bottke said he hopes the study serves as a conversation starter, getting scientists thinking about the planet-formation process in a more general sense...."

The way that the new models match what we can observe in the Solar system is exciting - and so is the uncertainty reflected in "that's just a guess." There's a lot yet to be learned - and now scientists have a new set of questions to ask.

Like this post? Tweet it: Tweet Or, not: your choice.

'Today the Sun, Tomorrow the Stars?' Weird-But-True Legal Claim

"Spanish Woman Claims She Now Owns Sun"
AFP, via myFOXOrlando (November 26, 2010)

"After billions of years the Sun finally has an owner -- a woman from Spain's soggy region of Galicia said Friday she had registered the star at a local notary public as being her property.

"Angeles Duran, 49, told the online edition of daily El Mundo she took the step in September after reading about an American man who had registered himself as the owner of the moon and most planets in our solar system.

"There is an international agreement which states that no country may claim ownership of a planet or star, but it says nothing about individuals, she added.

" 'There was no snag, I backed my claim legally, I am not stupid, I know the law. I did it but anyone else could have done it, it simply occurred to me first.'..."

This is going to be interesting.

The Lemming thinks that the 'no country may claim' agreement is the sort of thing that happened in the days when the United States and Soviet Union were the only countries with a serious chance of reaching the moon or any other planet. And when 'serious' thinkers who were still getting used to the 20th century didn't imagine that anybody would really want real estate that wasn't on Earth.

That was before Bigelow Aerospace, Virgin Galactic, and Spaceport America.

The folks who've staked their claims to nearby real estate may show a profit - after balancing lawyers' fees with whatever they get from Lunar Development Corporation, Martain Plains Industries, or whatever outfits doing the actual work are called by then.

And yes: The Lemming thinks there's a good chance that there will be a lively commercial interest in off-Earth properties within the lifetime of the folks mentioned in that article.

Somewhat-related posts:

• "Hyperbole, Business, and a Spaceship Factory"
  (November 19, 2010)
• "Bigelow Aerospace, Private Space Station, International Enterprise"
  (October 20, 2010)
• "Russia Will Have First* Commercial Space Station"
  (September 29, 2010)
• "Taxi to the Stars, No: To Earth Orbit, Soon"
  (June 5, 2010)
• "America's Seventh Spaceport"
  (January 19, 2010)
• "Asteroid Threat: Good News, We Have the Technology; Bad News -"
  (April 28, 2009)

More:

• "Humanity in Space: The Next Few Decades"

Venus Express, Atmospheric Surprise, and Orbits

"Venus' Atmosphere Proves a Real Drag, Leading to a Discovery "
Space.com (October 7, 2010)

"A spacecraft using a bold new method to study Venus — flying directly through the planet's atmosphere - has found that the atmosphere at Venus' poles is thinner than expected.

"The European Space Agency's Venus Express probe made the discovery during a series of dives through the atmosphere of Venus over the past two years. Scientists measured the drag on the spacecraft during these atmospheric dips to determine Venusian air density....

"...Venus Express has no instruments capable of measuring this density directly, researchers said. So mission planners have improvised. They sent the probe skimming down into the alien atmosphere on exploratory dives - at altitudes of about 110 miles (180 km) - in July-August 2008, October 2009, February 2010 and April 2010.

"During these jaunts, radio tracking stations on Earth watched for the drag exerted on the spacecraft. In addition, operators turned one of Venus Express' solar wings edge-on and the other face-on so that air resistance twisted the spacecraft, researchers said."

The Venusian atmosphere is 60% thinner than expected at the poles. Why? Good question: one that researchers don't have an answer for yet. It's not what they expected to find.

Which, as the Lemming has mentioned before, is at least as exciting as having predicted conditions confirmed by observations. This way, there's something new to learn.

There's something besides research going on with these dips into the atmosphere. The European Space Agency's Venus Express has been in an orbit that takes it quite a distance out from Venus. Far enough so that it has to fire its engines to correct for what the sun's gravity does to the orbit.

That takes fuel, which will run out in 2015 - according to the article. The mission planners are using these passages through the atmosphere to bring the orbit inward - reducing its orbital period from 24 hours to 12 hours.

They figure they'll have that done by 2012.

Ah, to be On Titan in the Spring

"Springtime for Northern Titan: Seven Years of Clearer Skies"
Space.com (September 24, 2010)

"The clouds are clearing on Titan as spring takes hold in its northern hemisphere, signaling a shift in the weather patterns on Saturn's largest moon, a new study finds.

"Titan is poised for a mostly sunny spring, one that will last seven Earth years, researchers have found. Seasons on Titan last so long because it takes the moon and Saturn about 30 years to orbit the sun. [New photo of Titan clouds.]

"Scientists analyzed data from the last six years of observations by NASA's Cassini spacecraft to piece together how Titan's weather cycle works. They found that conditions have changed since August 2009 - when the sun was directly over Titan's equator during its latest equinox..."

As the Lemming has written before, sometimes data shows that the mathematical models scientists developed to account for an earlier set of data don't fit what's really happening. Other times, they do. Either way, something's learned.

In this case, so far, it looks like the models are on the same page as the reality.

"...These findings match predictions by computer models developed by other researchers in the past. Rodriguez and his team combined those models with the actual Titan observations to understand Titan's evolving cloud patterns.

"Different cloud-formation mechanisms are likely at work in the different hemispheres, the researchers said...."

It a way, Titan is more like Earth than is Mars. Both worlds have a relatively thick atmosphere with lots of nitrogen, lakes, rivers, clouds and rain.

There are differences, of course:

"...Titan and its weather have intrigued scientists for decades. Some think Earth resembled Titan before life took hold — only not nearly as cold. Titan's surface averages 290 degrees below zero Fahrenheit (minus 179 degrees Celsius).

"Titan has a thick, nitrogen-rich atmosphere, and its surface features have been carved by the action of liquid hydrocarbons like methane, which is the chief component of natural gas here on Earth. Methane rain drizzles from Titan's clouds, pooling in frigid liquid lakes...."

Which brings up another point: Earth might have been more like Titan, only warmer, before runaway photosynthesis polluted this planet's atmosphere with that dangerously reactive gas, oxygen.

Sure: (Most) animals use oxygen these days - and (most) other organisms can endure it. But we're pretty sure it wasn't always that way. (April 9, 2010)

Change happens. And the Lemming is repeating himself again.

Related posts:

• "Life on Titan! Or, Not"
  (June 7, 2010)
• "Animals That Don't Need Oxygen - It Gets Weirder"
  (April 9, 2010)
• "Titan, Life Without Water, and 'Messing With Old Definitions' "
  (March 24, 2010)

Today's Venus is Cool: Relatively Speaking

"Hellish Venus Atmosphere May Have Had Cooling Effect"
Space.com (September 21, 2010)

"It may seem downright bizarre, but a new model of Venus' super-hot atmosphere suggests its greenhouse gases may actually be cooling the planet's interior.

"These gases initially cause Venus' temperature to rise, but at a certain threshold, they can trigger dynamic processes – which researchers call 'mobilization' – in the planet's crust that cool the mantle and overall surface temperature, researchers found...."

"...Noack and co-author Doris Breuer built a one-of-a-kind Venus computer model in which the planet's hot atmosphere was paired with a 3-D model of the interior.

"Unlike on Earth, Venus' high temperatures have a much bigger effect on the rocky surface, which ultimately loses its insulating qualities, the researchers said.

" 'It's a little bit like lifting the lid on the mantle: The interior of Venus suddenly cools very efficiently and the rate of volcanism ceases,' Noack said. 'Our model shows that after that "hot" era of volcanism, the slow-down of volcanism leads to a strong decrease of the temperatures in the atmosphere.'..."

Even today's 'cool' Venus is hot by our standards. The average surface temperature is 860 degrees Fahrenheit / 460 degrees Celsius.

The researchers' model shows that the current 'cool' Venus, with subdued volcanic activity - could still have active volcanoes in a few spots. Which is a pretty good match with what's been observed.

If the Noack - Breuer model is a fairly accurate description of how Venus has been shedding heat, this looks like a sort of feedback loop we see in our endocrine system - or the thermometer and furnace in houses.

2008 LC18 - Neptune Trojan Asteroid Discovered

"Asteroid Near Neptune Found in Gravitational Dead Zone"
Space.com (August 12, 2010)

"Astronomers have discovered a new asteroid in a region of Neptune's orbit where no previous object was known to exist -- a so-called gravitational 'dead zone.'

"The asteroid, which follows Neptune's orbit around the sun, may help shed light on fundamental questions about planetary formation and migration.

"The asteroid, classified as a Trojan, was found in a difficult-to-detect area near Neptune, known as the Lagrangian point L5. Lagrangian points are five areas in space where the gravitational tugs from two relatively massive bodies -- such as Neptune and the sun -- balance out. This allows smaller bodies, like asteroids, to remain stable and fixed in synch with the planet's orbit, as they orbit the sun. ..."

The article gives a pretty good look at what may be the start of a new wave of observations.

That phrase, "dead zone," in the title and first paragraph? It sounds cool, and probably encourages folks to read the article - but I think it's a bit more accurate to visualize the Lagrange points as invisible 'dips' in space-time where debris tends to collect.

Reading that, I think I see why the Space.com editors decided to go with "dead zone." It sounds much cooler.

I think the new asteroid is more intriguing than informative - at least for now. Astronomers think they'll be able to get a better idea of what happened as the Solar system developed, after studying this object. It's called 2008 LC18, by the way.

And others like it.

"...'We believe Neptune Trojans outnumber the Jupiter Trojans and the main-belt asteroids between Mars and Jupiter,' Scott Sheppard of the Carnegie Institution in Washington, D.C., told SPACE.com. 'If Neptune was where the main-belt was, we'd know thousands of these objects.'..."

I'd like to know why Scott Sheppard thinks there are that many Neptune Trojans: but I won't make snide cracks about his estimate. My guess is that the estimated count derives from what little astronomers have been able to learn of

"...'We estimate that the new Neptune Trojan has a diameter of about 62 miles (100 km), and that there are about 150 Neptune Trojans of similar size at L5,' Sheppard said. 'It matches the population estimates for the L4 Neptune stability regions.'..."

2008 LC18 is so far away - and, more to the point, so dim - that it's hard-to-impossible to tell what it's made of. Today. A few years from now? My guess is that it'll be a sort of race, to see whether someone gets a robot probe to 2008 LC18 before near-Earth telescopes get a clear look at the thing, and start analyzing its surface.

New Look at the Lost Ocean of Barsoom

"Ancient Mars Covered by Vast Ocean"
Space.com (June 13, 2010)

"More than 3 billion years ago, the northern plains of Mars were covered by a vast ocean that blanketed more than a third of the red planet's surface, new research suggests.

"Previous spacecraft investigations have pointed to possible signs of an ancient ocean on Mars. Still, this idea has been challenged for decades, as past evidence has been uncertain, and the matter remains one of the greatest open questions when it comes to researching the red planet.

"Now scientists have analyzed global databases of river valley networks on Mars, as well as deposits left behind by ancient deltas. Their research suggests 29 deltas they investigated -- more than half of all those in the databases -- sat at roughly the same height some 3.5 billion years ago, apparently ringing a vast ancient ocean shoreline in the northern lowlands of Mars...."


(B. Hynek, via Space.com, used w/o permission)

As more information and analysis adds up, it's looking more and more like that Mars looked a lot like that map - around 3,500,000,000 years ago.

"...'It is surprising how our results are compatible with previous independent studies based on totally different approaches,' [planetary geologist at the University of Colorado at Boulder, Gaetano] Di Achille said. 'Of course, our paper will not say the final word on the debate about the Martian ocean, but we are adding a significant piece to the big puzzle.'..."

There's a whole lot of discussion about where water was on Mars - and even if there was water there, to begin with. Assuming that Mars did have an ocean the size (roughly) of the Atlantic, billions of years ago, there's a big question: what happened to the water?

Which is why robotic Mars missions will - we hope - include tools to collect data that may help answer that question.

Related post:

• "Water on Mars: The Lost Ocean of Barsoom?"
  (November 23, 2009)

---

Other posts, about

• "Mars, Mostly"

More Earth-Like Worlds Than We Thought? Another Look

"Polluted Old Stars Suggest Earth-like Worlds May Be Common "
Space.com (April 12, 2010)

"Earth-like planets should be a fairly common feature of other solar systems in our galaxy, a new study of stellar senior citizens suggests.Earth-like planets should be a fairly common feature of other solar systems in our galaxy, a new study of stellar senior citizens suggests.

"More than 90 percent of stars in the Milky Way, including our own sun, end their lives as a white dwarfs. Traditionally, these dense stellar remains haven't been the first place that astronomers look for signs of planets outside our own solar system. Instead, exoplanet searches have focused on stars like our own sun.

"But tantalizing new results suggest that these elderly stars might also be a rich source of information on the potential for other planetary systems out there in the galaxy.More than 90 percent of stars in the Milky Way, including our own sun, end their lives as a white dwarfs. Traditionally, these dense stellar remains haven't been the first place that astronomers look for signs of planets outside our own solar system. Instead, exoplanet searches have focused on stars like our own sun...."

The short version, and an explanation for that "polluted old stars" headline, is that white dwarfs tend to have a whole lot more heavy elements in them than current models of stellar evolution say they should. They could have picked up these elements just by traveling through the interstellar medium for a really long time, but the mix of elements is hard to explain that way.

One of the simpler explanations is that quite a lot of rock fell on these stars, after they became white dwarfs. One of the places you're likely to get rocks is from planets and asteroids - which suggests that these old stars may have had planets at one time.

Since we go with the assumption that things change, but don't change all that much, it's not unreasonable to think that if a lot of stars had planets a long time ago, a lot of stars have planets now.

A closer look at some of these white dwarfs, to see if there are traces of oxygen on or around them, will have to wait until these researchers get time with the Hubble telescope.

I'm about as sure as I can be, that this isn't the final word on exoplanets. A few months ago another survey found evidence for fewer planets than expected. (January 9, 2010)

As I've said - a lot - these are interesting times.

Related posts:

• "Planets Found Circling Other Stars: 429 So Far"
  (February 15, 2010)
• ""Alien Dust," HD 131488, and the Puzzle of Planets"
  (January 15, 2010)
• "Early Returns From Galactic Census: Not As Many Planets as Expected"
  (January 9, 2010)

More:

• "A Serious Search for Other Worlds, Life, and - Maybe - Extra-Terrestrial Intelligence"

Planets Found Circling Other Stars: 429 So Far

"Out There: A Strange Zoo of Other Worlds"
Space.com (February 14, 2010)

"More than 400 worlds have been found beyond the reach of our sun, and the tally is rising rapidly. From super-Earths to giants dwarfing Jupiter, our galaxy is a zoo of different kinds of planets.

"Hot Jupiters

"The first discovery of an extrasolar planet around a sun-like star was 51 Pegasi B, an exoplanet roughly 50 light-years away, unofficially named Bellerophon after the tamer of the mythical Pegasus.

"Like many alien worlds found after it, 51 Pegasi B was a 'hot Jupiter,' a gas giant as close or closer to its star than Mercury is to our sun, unlike 'cold Jupiters' that orbit farther away such as Saturn or, naturally, Jupiter.

"Of the 429 exoplanets discovered to date, 89 have been hot Jupiters, likely because their large size and proximity to their stars makes them easier to spot by current techniques.

"Pulsar planets...."

Those aren't pulsars that are planets, but planets orbiting pulsars. They're pretty close to the 'there ain't no such animal' variety of observed phenomena.

Then there are

• Super-Earths
• Hot Neptunes
• Water worlds
• Chthonian planets
• Free-floating planets

Quoted in another blog:

"Not only is the universe stranger than we imagine, it is stranger than we can imagine."
Sir Arthur Eddington English astronomer (1882 - 1944)
(Drifting at the Edge of Time and Space (November 1, 2009)

The Space.com article is a pretty good overview of the sorts of planets we've found to date outside the Solar system: and ends with this:

"...An obvious hope is to find a Goldilocks planet just right for life — a planet at the right distance from its star to not roast or freeze and just the right size to retain an atmosphere but not so large as to become a gas giant. 'We're on a quest with a very high probability of success of finding a planet that's habitable or even inhabited with primitive life around other stars,' Beichman said. 'As we're progressing on that path, every time we round the bend along the way, we're finding fantastic new vistas.' "

Or not-so-primitive life.

The "Goldilocks Planet" May Not Be Like Earth

An intriguing possibility is that Earth isn't a "Goldilocks planet." What we've discovered about Mars and Venus suggest that our Earth may be about as small as a planet can be, and still have conditions that allow life. (December 5, 2009) We'll know more, when we've done a more thorough survey of this part of the Milky Way galaxy.

Related posts:

• "Second Smallest Exoplanet Found: HD 156668b (Caution! Geeky Content!)"
  (January 10, 2010)
• "Well, That's Interesting: The Evolution of Galaxies"
  Drifting at the Edge of Time and Space (February 8, 2010)
• "Probable Super-Earths Found: One Nearby"
  (December 14, 2009)
• "Earth May Not Be a 'Class M' Planet"
  (December 5, 2009)
• "Gliese 581: Lightest Known Expoplanet (Caution! Geeky Content!)"
  (April 21, 2009)

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Related posts, at

• "A Serious Search for Other Worlds, Life, and - Maybe - Extra-Terrestrial Intelligence"

Earth Exists: New Planetary Formation Model Explains Why

"How Earth Survived Its Birth"
Space.com (January 7, 2010)

"Just how Earth survived the process of its birth without suffering an early demise by falling into the sun has been something of a mystery to astronomers, but a new model has figured out what protected our planet when it was still a vulnerable, baby world.

"In short, temperature differences in the space around the sun, 4.6 billion years ago, caused Earth to migrate outward as much as gravity was trying to pull it inward, and so the fledgling world found equilibrium in what we now know to be a very habitable orbit.

"Planets like the Earth are thought to form from condensing clouds of gas and dust surrounding stars. The material in these disks gradually clumps together, eventually forming planetesimals – the asteroid-sized building blocks that eventually collide to form full-fledged planets.

So far, so good: that's pretty much what astronomers and planetary scientists have figured for some time now. There's just one catch to this established model, and it's a big one.

The math says that as planets form, they also migrate inside the disk of dust. Specifically, the math says they migrate towards the star. Then they fall in. According to the mathematical models.

Obviously, since I've written this post, and you're reading it, there's something wrong with this picture. Earth is rather definitely here, philosophy 101 freshman-baiting notwithstanding.

Or, as one of the astronomers put it:

"...'Well, this contradicts basic observational evidence, like We. Are. Here,' said astronomer Moredecai-Mark Mac Low of the American Museum of Natural History in New York...."

The existing mathematical models didn't take temperature differences within the dust disk into account. Turns out, the disk is opaque - and quite a bit hotter near the star. Factor that into the equations, and you don't have Earth falling into the sun a bit over 4,000,000,000 years back.

The new mathematical models predict that planets are pulled in - just like in the earlier models - and that temperature differences push them away from the star. Each planet, again in the newer model, reaches an equilibrium point where its orbit stays stable - and eventually the dust dissipates.

Wait a few billion years, and you've got trilobites, dinosaurs - and us.

Since the model that Mac Low and his colleagues came up with doesn't have Earth plunging into the sun long before life got started, it would seem that it's a closer match with reality than previous ones.

Particularly since it's becoming quite obvious that stars with planets orbiting them aren't anywhere near the 'chicken teeth' rarities they were supposed to be, not all that many decades back. (But aren't as common as they might be, either - More about that, tomorrow morning.)

Exciting times, these that we live in.

---

Related posts, at

• "A Serious Search for Other Worlds, Life, and - Maybe - Extra-Terrestrial Intelligence"

Outer Solar System: More Planets? And What to Do With Them

"Earth-Sized World Could Lurk in Outer Solar System"
Space.com (January 4, 2010)

"Some astronomers say that a planet the size of Mars or Earth could be lurking on the fringes of our solar system. But even the latest space telescopes that launched in 2009 stand little chance of finding such a distant object.

"Such a world, if it exists, would probably have an orbit far beyond Pluto or similar dwarf planets in the outer solar system. It would likely resemble a frozen version of Mars or Earth at best, a most unsuitable home for life. And it would not be alone.

" 'When the solar system's story is finally written, it's much more likely that it will have closer to 900 planets rather than the nine that we grew up with,' said Alan Stern, a planetary scientist at the Southwest Research Institute (SwRI) in Boulder, Colo...."

"Finally written?" That may take a while. ("Once it Was Believed / Now We Know" Brian H. Gill (2003))

Anyway, this article is an interesting look at what we know, and don't know, about the outer reaches of the Solar system.

"...[Caltech astronomer Mike] Brown noted that any future discovery of larger objects in the outer solar system would either suggest that scientists have the wrong idea of how planets form, or might indicate that the early solar system had more material available than previously suspected.

" 'More interesting to me, though, is that it would be an entirely new class of large body,' Brown said. 'We don't have any ice rich planetary-sized bodies in the solar system, so we don't really know what they would be like and how they would work.'

"[Southwest Research Institute planetary scientist Alan] Stern has long supported the idea of many planet-sized lurkers in the outer solar system. He referred to computer models that show how medium-sized planets might have formed during the chaotic creation of gas giants such as Jupiter, when swirling smaller pieces clumped together to form larger bodies...."

Looks like it's another case of current mathematical models for how the cosmos works being pretty close matches to reality - or not. Either way, it's exciting.

The article brings up the ongoing debate about what a "planet" is - exactly. I have a notion that's going to be going on for quite a while. Me? I think if it's round, doesn't either have fusion going on inside or is a star that ran out of fuel, and isn't orbiting something else that's round and isn't a star - it's a planet. That would include 'brown dwarfs' - so there would have to be an upper mass limit, too: which would be somewhat arbitrary. Jupiter, arguably, is a brown dwarf in relatively close orbit around Sol.

Like the fellow said:

"Not only is the universe stranger than we imagine, it is stranger than we can imagine."
Sir Arthur Eddington English astronomer (1882 - 1944)

Finally, besides 'pure science' and the joy of discovery, I think there are some exciting possibilities in those possible planets.

If one is big enough, and mostly rock and metal, like the inner planets (Mercury through Mars, maybe Ceres): it could be moved in, warmed up, and terraformed. There are stable points in the inner Solar system: 60 degrees away from Earth, ahead and behind in our orbit, for starters.

Granted, right now we can't move planets around. But there's nothing in physics that says it's impossible: it just takes more energy than we can handle right now. I've gotten used to the idea that nothing - technology included - stays the same. And growing up when computers and interplanetary spaceships with robot explorers weren't a part of everyday life gives me a certain perspective.

Terraforming is taking a planet and modifying it until it's a reasonable facsimile of Earth. It's another thing we can't do - now - but probably could, after we work out technical details.

Since it seems a little more likely that what we found outside the orbits of Neptune and Pluto/Charon will be more frozen water and other volatile substances than rock and metal, moving one and terraforming it may not be practical.

Unless we figure out how to transmute elements on a planetary scale. We can change lead to gold now, on a very small scale - but it costs too much to be a commercially viable process. I'm getting off-topic.

Where was I? Frozen slushballs. Right.

If we find something, say, the size or Ceres of Mars, made mostly of water ice and frozen methane, hydrogen, and other substances that are normally gas or liquid at "normal" temperatures, that could be moved in and used as a reservoir for terraforming Mars or Venus.

Of course, comets are falling in toward the sun at a fairly steady rate: so there wouldn't really be any point.

That article in Space.com? It's a pretty good look at where we are at, studying the outer Solar system.

Related posts:

• "Pandora? Yeah: It Could Exist, Based on What We Know"
  (December 29, 2009)
• "Another Super-Earth: Probably With Water, Possibly With Strange Chemistry"
  (December 17, 2009)
• "Earth May Not Be a "Class M" Planet"
  (December 5, 2009)
• "Water on Mars: The Lost Ocean of Barsoom?"
  (November 23, 2009)
• "Another Hot Jupiter With Organic Compounds"
  (October 21, 2009)
• "A Serious Search for Other Worlds, Life, and - Maybe - Extra-Terrestrial Intelligence"
  (May 29, 2009)
• "The Caves of Mars"
  (October 26, 2009)
• "Cloud Cities of Venus"
  (July 25, 2008)

---

More in this blog:

• "Change, American Culture, Trilobites, Humanity's History, and the Big Picture"
  (Last updated December 21, 2009)
• "Mars, Mostly

Related posts, at

• "A Serious Search for Other Worlds, Life, and - Maybe - Extra-Terrestrial Intelligence"

Pandora? Yeah: It Could Exist, Based on What We Know

"Moons Like Avatar's Pandora Could Be Found"
Space.com (December 27, 2009)

"The new science fiction blockbuster 'Avatar' is set on habitable and inhabited moon Pandora, which orbits the fictional gas giant Polyphemus in the real Alpha Centauri system.

"Although life-bearing moons like Pandora or the Star Wars forest moon of Endor are staples of science fiction, astronomers have yet to discover any moons beyond our solar system. However, they could be science fact, and researchers might soon not only be able to spot them, but also scan their atmospheres for key signs of life as we know it, such as oxygen and water.

" 'If Pandora existed, we potentially could detect it and study its atmosphere in the next decade,' said astrophysicist Lisa Kaltenegger of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass...."

That word, "potentially," covers a lot of ground. According to the article, the next-generation James Webb Space Telescope's system could analyze a moon's atmosphere - if the moon and its planet passed between their star and Earth at intervals. My guess is that the odds aren't particularly good for the host planet's orbit to line up like that.

On the other hand, with hundreds of known planets orbiting other tars - and more being found on a fairly regular basis - it's not at all impossible that we'd find a transiting planet-moon system orbiting another star.

The Space.com article does a pretty good job of discussing what it would take for the moon of a gas giant to be habitable, based on what we know about radiation belts and tidal forces in the neighborhood of worlds like Jupiter Saturn.

More about the setting of Avatar:

• "The Real Science of 'Avatar' "
  Space.com (December 21, 2009)

Sort-of-related posts:

• "Beautiful Space Princesses, Almost Certainly Not: Flying Whales, Maybe"
  Drifting at the Edge of Time and Space (December 8, 2009)
• "Really Old Dust Grains, a Galactic Collision, and a Lively Interest in God's Creation"
  A Catholic Citizen in America (August 10, 2009)

Related posts, at

• "A Serious Search for Other Worlds, Life, and - Maybe - Extra-Terrestrial Intelligence"

Water on Mars: The Lost Ocean of Barsoom?

"New Map Bolsters Case for Ancient Ocean on Mars "
Space.com (November 23, 2009)

"Several lines of evidence point to the possibility of a past ocean on Mars, from apparent ancient shorelines to chemicals in the soil.

"Add to the list a new map of the red planet's valley. The map shows extensive valley networks around the equator and in the southern hemisphere, suggesting a warmer mars long ago, with extensive rainfall that would have feed an ocean in the northern hemisphere.

" 'All the evidence gathered by analyzing the valley network on the new map points to a particular climate scenario on early Mars,' Northern Illinois University geography professor Wei Luo said. 'It would have included rainfall and the existence of an ocean covering most of the northern hemisphere, or about one-third of the planet's surface.'

"The valley networks are more than twice as extensive (2.3 times longer in total length) than had been previously mapped out...."

There's a bit more detail in the article, about the data and how it was analyzed. I think that a scientist, who said that a single large northern ocean on Mars - a very long time ago - would explain patterns that are emerging as we study drainage channels that are still visible.

On the other hand, there's a big question that I'm not sure has been answered yet: why do Mercury, Venus, Earth and Mars all have the same general sort of terrain? A section of lowlands, and a section of highlands. On Earth, the lowlands are filled with a water-salt solution that we call oceans. Venus and Mars don't have that much water - now. Mercury probably never did.

Even more interesting, Venus - and even Mars - seem to have fairly clearly-defined continents. ("Venus Continents," "Exploratour - Comparing the Surfaces of Earth and Mars," Windows to the Universe^{Windows to the Universe®}, University Corporation for Atmospheric Research (UCAR). © The Regents of the University of Michigan)

"Just Add Water?"

If someone put a tub of liquid water on Mars, the air there is so thin that it would quickly boil away - cold as it is. Venus isn't much better as a vacation spot: it's hot enough to melt lead in some places on the surface.

Still, Venus does have continents: two larger ones, Ishtar Terra, and Aphrodite Terra. Ishtar Terra is near the north pole and none too large, really - roughly the size of the continental United States. Aphrodite Terra is near the equator and about half the size of Africa. There are two other highland/continental regions: Alpha Regio near the equator, and Beta Regio in the southern hemisphere.

As things stand, nobody's likely to walk on Venus. Not anytime soon. On the other hand, if we thinned out the atmosphere of Venus, cooling the place off in the process, introduced water and plants to start producing oxygen, after a while we'd have a planet that looks a little like Earth.

I wouldn't live to see it: but some cultures are able to plan projects that span generations. And, in the meantime, we just might be able to float cities in the clouds of Venus. ("Cloud Cities of Venus ," (July 25, 2008))

As for Mars, if or when we do settle the place, it'll probably be easier to make micro-habitats, instead of trying to terraform the whole planet in one go. Besides, there's a lot to study on Mars, just the way it is.

---

Other posts, about "Mars, Mostly."

Lumps in the Rings of Saturn

"Surprising, Huge Peaks Discovered in Saturn's Rings "
Space.com (September 21, 2009)

"Stunning new views of Saturn from a NASA spacecraft have revealed odd formations in the planet's trademark rings, including ripples as tall as the Rocky Mountains.

"The new images taken by NASA's Cassini spacecraft show that Saturn's icy rings - once thought to be relatively thin - can be miles thick in some points and include weird, bright streaks from clouds kicked up by the cosmic clash between ring particles and interloping space debris.

" 'It's like putting on 3-D glasses and seeing the third dimension for the first time,' said Bob Pappalardo, Cassini's project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., in a statement. 'This is among the most important events Cassini has shown us.'

"Cassini recorded the new images of Saturn in the week surrounding the planet's Aug. 11 equinox, a time when its bright bands of rings are edge on to the sun and nearly invisible as seen from Earth...."

This is a pretty big deal.

"...'We thought the plane of the rings was no taller than two stories of a modern-day building and instead we've come across walls more than 2 miles [3 kilometers] high,' said Cassini imaging team leader Carolyn Porco at the Space Science Institute in Boulder, Colo....

"One ripple rises nearly 2 1/2 miles (4 km) above the plane of Saturn's rings. The big blip is caused by the gravitational tug of the planet's moon Daphnis. It is the highest peak among the rings, mission managers said...."

These miles-high ripples in the rings apparently are easier to detect when the rings are edge-on to the sun: something that hasn't happened since the last Saturnian equinox, about fifteen years ago. This time, we've got a robot out there: orbiting Saturn. Cassini has been there since October of 1997. (Moon and Planets Exploration Timeline, Space Today Online)

Previous Saturn missions were flybys, where spacecraft whip past planets, gathering as much information as possible. Missions like that are valuable, revealing new details, but sort of like a whirlwind tour of Europe: When it's over, you've got a lot of pictures, a lot of information, some general impressions - but not the sort of knowledge that comes from sticking around for a while.

The Space.com article has four photos - three of the new features.

Planets Collided - Recently - Around a Star Called HD 172555

"Two Worlds Collide in Deep Space"
Space.com (August 10, 2009)

"Two distant planets orbiting a young star apparently smashed into each other at high speeds thousands of years ago in a cosmic pileup of cataclysmic proportions, astronomers announced Monday.

"Telltale plumes of vaporized rock and lava leftover from the collision revealed its existence to NASA's Spitzer Space Telescope, which picked up signatures from the impact in recent observations.

"The two-planet pileup occurred within the last few thousand years or so - a relatively recent cosmic timeframe. The smaller of the two bodies - a planet about the size of Earth's moon, according to computer models - was apparently destroyed by the crash. The other was most likely a Mercury-sized-planet and survived, albeit severely dented...."

The planets weren't, from one point of view, in 'deep space.' They were orbiting the star HD 172555, about 100 light-years from Earth. The star - and its planets - are around 12,000,000 years old, compared to the Solar system's 4,500,000,000 years.

Astronomers figure that they hit at around 22,400 miles an hour, or 10 kilometers per second: fast enough to produce a great deal of heat. At this point, there's quite a bit of "amorphous silica rock" (melted glass), tektites, and clouds of silocon monoxide gas orbiting HD 172555 - along with the surviving planet.

Yeah, it's Kind of a Big Deal

This sort of collision is, assuming that current theories of how planetary systems form, fairly common. The Hellas Basin on Mars, what we're discovering about Mercury, the odd way Venus and Uranus, and the currently least-unlikely explanations for how Earth's moon got there all indicate that there were a lot of collisions around here. Happily, that's about 4,000,000,000 years in the past now.

And, although they're presumably fairly common, these collisions happen fast. Spotting debris from one that happened maybe a few thousand years ago is a rare opportunity - particularly since it's so close. Cosmically speaking, that is.

The Space.com article gives a pretty good look at what's been observed, and why it's important.

Background and related articles:

• "Oh, My! When Worlds Really Collide"
  Space.com (September 23, 2008)
  • (BD+20 307, about 300 light years away)
  • Background on that planetary system at: "The Wayback Machine? Nearby Solar System Looks Like Home"
    Space.com (July 25, 2005)
• "How the Moon Was Made: Cosmic Collision"
  Space.com
  video 2:40

---

Related posts, at

• "A Serious Search for Other Worlds, Life, and - Maybe - Extra-Terrestrial Intelligence"

Jupiter Imact: Hubble Took a Look

"Hubble Telescope Photographs Jupiter Impact Site"
Space.com (July 24, 2009)

"The unexpected impact of some space object with Jupiter, creating a dark bruise in the gas giant's atmosphere, proved a tempting enough target for scientists to put a hold on testing out the revamped Hubble Space Telescope and use its new camera to capture an image of the rare event.

"The plan, first reported by Spaceflight Now, was carried out yesterday so that astronomers could use the 19-year-old Hubble's unique capabilities to get an image of the spot, probably caused by a comet, before too many days had passed since the impact and Jupiter's atmosphere distorted the shape.

"The new Hubble image, released today, [Friday] shows a lumpiness to the debris plume caused by turbulence in Jupiter's atmosphere. The image is a natural color image of Jupiter in visible light...."

The dark patch is roughly the size of the Pacific Ocean, it seems. Which is pretty close to the headline I mentioned in an earlier post, saying that the hole in Jupiter's clouds was the size of Earth. Seen from space, the Pacific Ocean covers most of one side of this planet.

Why use Hubble? It gives the best, sharpest, look at Jupiter in visible wavelengths of any available telescope. "...Hubble managers decided that the impact event was rare enough and important enough to pause testing to get a look...."

This article gives a pretty good overview of what Hubble's observed, and what we know about the event on Jupiter. For one thing, the energy released in the impact was thousands of times more than what we experienced in the Tunguska event, back in 1908.

I've written before, about the prudence of setting up defenses before something leaves an ocean-size splat-mark on Earth.

Meanwhile, there's a lot to learn from that impact on Jupiter.

Related posts:

• "Big Impact on Jupiter: Astronomers' Field Day"
  (July 21, 2009)
• "Life Could Have Survived Earth's Late Heavy Bombardment"
  (May 24, 2009)
• "It Seems it Took More Than an Asteroid Hit to Finish the Dinosaurs"
  (April 29, 2009)
• "Asteroid Threat: Good News, We Have the Technology; Bad News -"
  (April 28, 2009)
• "Earth Day 2009: Don't Stop Breathing to Save Earth"
  (April 22, 2009)
• "Ten Not-So-Trivial Facts About Earth"
  (February 16, 2009)
• "How to Destroy Earth (It Ain't Gonna be Easy)"
  (July 9, 2008)
• "No Magnetic Field (to Speak of) For Mars: Asteroid Implicated"
  (May 12, 2009)

Big Impact on Jupiter: Astronomers' Field Day

"Jupiter Apparently Smacked by Rogue Object, New Images Reveal "
Space.com (July 20, 2009)

"Jupiter has apparently been smacked again by a rogue object hurtling through space, new images from amateur astronomers and NASA reveal.

"A giant scar-like blemish has appeared in the clouds near Jupiter's south polar region, which NASA observed in infrared after receiving a tip from an amateur skywatcher in Australia. The likely impact appears to have occurred exactly 15 years after the remnants of Comet Shoemaker-Levy 9 bombarded the planet in 1994 in an event that was widely predicted and scrutinized as it happened.

"The latest impact was not predicted, and it was caught by chance...."

The impact was discovered by an Australian amateur astronomer, Anthony Wesley, 44, who makes a living as a computer programmer. Situations like this, where an amateur astronomer is the first to notice a new phenomenon, aren't all that rare. Professional astronomers are paid to use their very expensive installations to watch places that are known to have valuable data. It's the amateurs who are everywhere else, ready to notice when something unexpected shows up.

Anthony Wesley almost missed this impact.

"...In an observation report posted to his Web site, Wesley said he almost missed spotting Jupiter's new blemish entirely because he was tired after a late-night skywatching session.

" 'It was a very near thing,' he wrote, adding that by 1 a.m. Local Time, he decided at the last minute to keep observing for another half hour.

" 'I'd noticed a dark spot rotating into view in Jupiter's south polar region and was starting to get curious,' Wesley went on. 'When first seen close to the limb (and in poor conditions) it was only a vaguely dark spot, I thought likely to be just a normal dark polar storm. However as it rotated further into view, and the conditions also improved, I suddenly realized that it wasn't just dark, it was black in all channels, meaning it was truly a black spot.'..." (Space.com)

The Space.com article is one of the first to take note of the July 19, 2009, impact on Jupiter. I've put links to several of the more recent articles toward the end of this post. The Space.com article is more detailed than many - although Today's CNN article does a pretty good job of passing details along.

A Bunch of Astronomers Looking at Jupiter: So What?

It's been 15 years since Comet Shoemaker-Levy 9 hit Jupiter. That was a scientific bonanza: since the comet had been tracked before impact, and the time and place of the impact was predicted, astronomers had a chance to set up an impressive array of sensors to record the event.

And, since it happened on Jupiter, the effect on Earth was somewhere between negligible and non-existent - as far as we know.

This impact was on Jupiter, again, but it wasn't predicted. Mr. Wesley didn't know he'd be giving the heads-up to professional astronomers a couple days ago.

Big Impact of Jupiter: Fascinating, but Not Earth-Shattering

Having the second big impact in 15 years happen on Jupiter isn't such a surprise. Jupiter is the biggest planet, in terms of diameter - and is vastly heavier than anything else in the Solar System except for the sun. Decades ago, someone referred to the planetary system we're in as being 'the sun, Jupiter, and debris.'

So, between being a big target and having a whacking great gravitational field to pull assorted rocks and ice balls in, being fairly close to the asteroid belt, and having an orbit that comets sometimes cross on their way to the sun, Jupiter is going to have big, heavy things falling on it fairly often.

What's a little disturbing about this latest impact is it wasn't predicted. Nobody noticed something approaching Jupiter before an Earth-size hole was blasted in the upper cloud decks.

Asteroid Impact Here? Still Not Earth-Shattering - But We Wouldn't Like it

I don't know enough physics to say what sort of energy is needed to punch a hole thousands of miles wide in Jupiter's upper cloud layers: but my guess is that I wouldn't want to be anywhere nearby when energy on that scale is released.

And, since Earth is only about 8,000 miles across, if something like what hit Jupiter last Sunday came down in, say, Antarctica, anywhere on Earth would be "nearby."

An event like that would push news about floods in Mongolia off the front page. It would probably even eclipse coverage of Michael Jackson's death. And, humanity would have a great deal more to worry about than getting ready for the Olympic Games next year.

I'd rather not find out whether or not there would be people around, ten thousand years after such an impact. Cockroaches, though, almost certainly would be. They've been through quote a few hard times on Earth.

We Have the Technology to Protect Ourselves

I was mildly surprised to discover that The Spaceguard Foundation was organized in 1996. I'd expected to find an earlier founding date. Serious discussions among and loose associations of astronomers concerned with tracking objects that might hit Earth go back decades.

We've got the technology to detect (most) largish objects that might hit Earth, track their orbits, and make pretty-good estimates of when and where they might hit. As they got closer, we'd be able to make increasingly accurate predictions.

We've also got the technology to do something about a big rock, or gravel pile, or slushball, headed our way. The relative merits of moving the incoming object so that it misses Earth, or breaking it up so that it hits, but in small pieces over a large area, have been discussed.

The 'breaking it up' scenario isn't, necessarily, as crazy as it may sound. Earth gets hit by around 2,000 tons of meteor every day. (Journal of the Royal Astronomical Society of Canada, via Harvard) Except for a few astronomers, we don't notice all those tons of stuff falling on our heads, because most of it burns up in the upper atmosphere.

My guess is that adding more tonnage would make a measurable difference, somehow. And, that it would result in a spectacular one-time-only meteor shower. And, in America, several thousand lawsuits for everything from emotional suffering to a disappointing vacation.

Earth and Asteroids: We've Been Lucky, So Far

I'd like to think that outfits like The Spaceguard Foundation will distract national leaders from whatever it is that they usually do long enough to get an effective detection and interdiction force in place. Before something like the Tunguska Event happens over someplace like Singapore or Dallas.

Related posts:

• "Life Could Have Survived Earth's Late Heavy Bombardment"
  (May 24, 2009)
• "It Seems it Took More Than an Asteroid Hit to Finish the Dinosaurs"
  (April 29, 2009)
• "Asteroid Threat: Good News, We Have the Technology; Bad News -"
  (April 28, 2009)
• "Earth Day 2009: Don't Stop Breathing to Save Earth"
  (April 22, 2009)
• "Ten Not-So-Trivial Facts About Earth"
  (February 16, 2009)
• "How to Destroy Earth (It Ain't Gonna be Easy)"
  (July 9, 2008)
• "No Magnetic Field (to Speak of) For Mars: Asteroid Implicated"
  (May 12, 2009)

In the news:

• "Mystery impact leaves Earth-size mark on Jupiter"
  CNN (July 21, 2009)
• "Jupiter 'struck by large object' "
  BCC (July 21, 2009)
• "Jupiter Struck by Object, NASA Images Confirm"
  Reuters, Via FOXNews (July 21, 2009)

Background:

• The Spaceguard Foundation
  Nec cum fiducia inveniendi
  Nec sine spe
  • This is the mirror site hosted by Harvard. There are at least two others, in
    • Europe (Italy)
    • Japan
• "Meteor News (A Size Classification of Meteoritic Material Encountered by the Earth)"
  Millman, P. M., Journal of the Royal Astronomical Society of Canada, Vol. 46, p.79, via Harvard