At his Psychology Today blog, Michael Chorost delves into a question about exoplanets that I've not really thought much about before — how easy they would be to leave.
Many of the potentially habitable exoplanets that we've found — the ones we call "Earth-like" — are actually a lot bigger than Earth. That fact has an effect — both on how actually habitable those planets would be for us humans and how easily any native civilizations that developed could slip the surly bonds of gravity and make it to outer space.
The good news, says Chorost is that the change in surface gravity wouldn't be as large as you might guess, even for planets much bigger than Earth. The bad news: Even a relatively small increase in surface gravity can mean a big increase in how fast a rocket would have to be going in order to leave the planet. It starts with one equation — SG=M/R^2.
Let’s try it with [exoplanet] HD 40307g, using data from the Habitable Exoplanet Catalog. Mass, 8.2 Earths. Radius, 2.4 times that of Earth. That gets you a surface gravity of 1.42 times Earth.
... it’s amazingly easy to imagine a super-Earth with a comfortable gravity. If a planet had eight Earth masses and 2.83 times the radius, its surface gravity would be exactly 1g. This is the “Fictional Planet” at the bottom of the table. Fictional Planet would be huge by Earth standards, with a circumference of 70,400 miles and an area eight times larger.
Does that mean we could land and take off with exactly the same technology we use here, assuming the atmosphere is similar? Actually, no. Another blogger, who who goes by the moniker SpaceColonizer, pointed out that Fictional Planet has a higher escape velocity than Earth. Put simply, escape velocity is how fast you have to go away from a planet to ensure that gravity can never bring you back. For Earth, escape velocity is about 25,000 miles per hour. Fictional Planet has an escape velocity 68% higher. That’s 42,000 miles per hour.
Thanks to Apollo 18, who also helped with the math for Chorost's post.
I really enjoyed reading a recent story in The New York Times Magazine about attempts to understand extreme longevity — the weird tendency for certain populations to have larger-than-average numbers of people who live well into their 90s, if not 100s.
Written by Dan Buettner, the piece focuses on the Greek island of Ikaria, and, in many ways, it's a lot like a lot of the other stories I've read on this subject. From a scientific perspective, we don't really understand why some people live longer than others. And we definitely don't understand why some populations have more people who live longer. There are lots of theories. Conveniently, they tend to coincide with our own biases about what we currently think is most wrong with our own society. So articles about extremely long-lived populations tend to offer a lot of inspiring stories, some funny quotes from really old people, and not a lot in the way of answers.
Buettner's story has all those elements, but it also proposes some ideas that were, for me, really thought provoking. After spending much of the article discussing the Ikarian's diet (it's low in meat and sugar, high in antioxidants, and includes lots of locally produced food and wine) and their laid-back, low-stress way of life, Buettner doesn't suggest that we'll all live to be 100 if we just, individually, try to live exactly like the Ikarians do. In fact, he points out that other communities of long-lived individuals actually live differently — Californian Seventh-Day Adventists, for instance, eat no meat at all and don't drink, and they live with the normal stresses of everyday American life.
What these groups do have in common, though, is a strong social infrastructure that ties people to each other emotionally and connects individual choices to a bigger community lifestyle.
Read the rest
The Curiosity rover can do a lot of things, but nobody is expecting her to find direct evidence of life on Mars. In fact, the hunt for life on the Red Planet has been a pretty stunted one. The last time we really looked was during the Viking missions, which tried to find chemical "footprints" that would exist if there had once been life on Mars, but that could end up on that planet for other reasons, as well. What we got back was a less-than-enthralling "Outlook Hazy. Try Again Later."
Ever since, we've contented ourselves with searching for indirect evidence — assessing the planet for signs that it might once have had the conditions necessary for life to happen. That's important, and it will make direct evidence of life more believable if we ever do find it, but it's not quite the same thing.
But now, DNA sequencing tools have become portable enough (and drilling technology has become powerful enough) that some scientists and Craig Ventner think we could send a probe to Mars which could find buried traces of actual DNA protected in the dirt and sequence that DNA on site.
It's also possible that life hitched a ride between Earth and Mars in their early days. Asteroid impacts have sent about a billion tonnes of rock careering between the two planets, potentially carrying DNA or its building blocks. That could mean that any genetic material on Mars is similar enough to DNA that we have a chance of finding it using standard tests.
Even if we don't, we can set up future sequencers to look for molecules that use alternative sugars or chemical letters in the genetic code. "We're not there yet, but it's not a fundamental limitation," says Chris Carr of the Massachusetts Institute of Technology, who works on the NASA-backed Search for Extraterrestrial Genomes.
Remember arsenic life? In 2010 NASA researchers thought they'd found evidence that certain bacteria could use arsenic in their DNA where all other forms of life on Earth use phosphate. Then it turned out their research was really flawed. Then it turned out they were wrong. In general, there was a to-do.
Fast forward to this month, when scientists from the Weizmann Institute of Science in Rehovot, Israel published a study in which they were trying to figure out how bacteria can tell the difference between phosphate and arsenate and "know" to prefer the phosphate. They used phosphate-collecting proteins from four different species of bacteria in their research, including the one that had been at the center of the arsenic life controversy. And along the way, they discovered a fun twist to that story.
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When I was about 10, I developed an obsessive love for The X-Men. It started with the Saturday morning cartoon show, but quickly became about comic books, as well. To this day, long-overwritten plot points from the Marvel universe take up a significant portion of my memory space (as my husband can attest). In my marriage, I am the one who is called upon to flesh out the backstory and conflicts with source material after my husband and I have seen an action-hero movie.
But I didn't own a single comic book until I was 19.
In fact, I'm not sure my parents or friends even knew I liked comic books. All my reading, for nine years, was done in secret. I'd slip into the comic book aisle at the bookstore when nobody was around to see, grab an anthology off the shelf, and spend the next two hours nestled in a corner somewhere — with the comics safely hidden behind a magazine or large book. I did the same thing at the public library. Never even checked one out. If I couldn't finish a library comic anthology in one afternoon, I'd hide it in a seldom-used section and come back the next day. (My apologies to the librarians of the world for that.)
Partly, that shame and fear came was about being labeled a nerd, in general. But there was, for me, also a pretty heavy gender component. Tall, clumsy, nerdy, ignorant of fashion or makeup, and definitely not "attractive" in the way that sheltered pre-teen and teenage society defines it, I spent a good chunk of my adolescence paranoid about my identity as a female. Where and when I grew up, there weren't a lot of good role models for diversity of female experience. My parents always supported who I was, but society and my peers seemed to have a pretty strict definition of who girls were and what they liked ... and I didn't fit. Admitting that I was into comics felt like it would be just one more thing I did wrong. That's why I really, really love Women Reading Comics in Public Day, an unofficial holiday started by the bloggers at DC Women Kicking Ass.
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A couple of days ago, Rob told you about scientists who had built a "jellyfish" in the lab, using rat cells. Which is awesome. Naturally, it's not quite as awesome as it sounds, though.
The scientists haven't created life. Instead, they've built a little construct of cells and silicone. This construct—the medusoid—is interesting, in that, when you spark it with electricity, it moves in ways that are very similar to a juvenile jellyfish. But it's not actually an animal. It doesn't eat. It can't make more of itself. It needs that outside zap to move at all.
But despite all that it is not, the medusoid is a very cool first step towards doing some amazing things. At Scientific American, journalist Ferris Jabr looked at what the scientists have done, how living jellyfish work, and what it would take to build a for-real-real artificial jellyfish.
Whereas a real jellyfish generates electrical impulses to stimulate its muscle cells, a medusoid is entirely dependent on voltage generated by electrodes in its tank. Moon jellies have eight pacemaker cells scattered around the middle of their bodies (just about every jellyfish body part comes in multiples of four). Pacemaker cells keep the jellies’ muscles pulsating rhythmically. We have pacemaker cells in our hearts that do the same thing. So do rats. Janna Nawroth thinks it’s possible to weave pacemaker cells from a rat’s heart into the heart muscle tissue that makes up a medusoid, which might allow the artificial jellyfish to bob on its own, sans electrodes.
The upgrade would rely on a technique known as “co-culturing,” in which different types of cells are grown together. It’s often difficult enough to get one cell type to live happily in the lab, let alone a mixture of different kinds of cells. Think of them as high-maintenance houseplants that are fussy about their neighbors, withering if they do not like their circumstances. Although scientists have not yet mastered co-culturing, they have made impressive advances, cultivating little gardens of gut tissue and bacteria, for example, as well as epithelial cells and immune system cells.
The Life's Little Mysteries blog is in the midst of a string of posts that are, basically, like Marvel Comics "What If?" series as applied to the scientific history of Earth.
For example: What if humans had evolved to include more than two sexes, or to need three or more sex cells in order to procreate? What if Pangea (everybody's favorite supercontinent) had never split into chunks? What if Earth had never been in a massive collision with another, huge space object—meaning, what if the Moon didn't exist?
Now, if you've read very many of the comics you know that the answer to "What If?" is almost always "everybody dies". This series of posts is a bit less fatalistic. But, still, the point is made—these changes would radically alter life as we know it, and not necessarily in ways that sound like a lot of fun.
Take that question about the Moon. The implications of a Moon-less Earth are farther-reaching than you might guess:
Huge tides generated by the moon – which orbited much closer to Earth when it formed – washed the chemical building blocks for life from land into the oceans and helped "stir up the primordial soup," said Neil Comins, a professor of physics at the University of Maine.
The moon's gravity has helped slow Earth's rotation from an initial six-hour day to our current 24-hour day, while also stabilizing the tilt of our planet's axis, and thereby moderating the seasons. Life forms on a moonless Earth would therefore have different patterns of activity per the short days and nights, Comins told Life's Little Mysteries. These creatures might need to migrate more frequently to cope with extreme climate swings as well.
In Before the Lights Go Out, my new book about the future of energy, I made a joke about the formation of fossil fuels that I would like to rescind.
"All three fossil fuels come from the same place—ancient plants and animals that died and were buried beneath layers of earth and rock, often millions of years before dinosaurs roamed this planet. (That's right. Oil isn't made from dinosaurs. But an apatosaurus makes a better corporate mascot than a phytoplankton does.)"
After watching this video about the secret lives of plankton, produced by TEDEducation and marine biologist Tierney Thys, I feel that the above statement is in error. Clearly, plankton—including phytoplankton, which are just tiny plants, as opposed to zooplankton, which are tiny animals—would make excellent mascots. Somebody at Standard Oil really dropped the ball on this one.
Side Note: I found this video through a link to The Kid Should See This, a blog that aggregates kid-friendly wonders from science, art, technology, and more. If you aren't reading it, you should be. Even if you don't have kids.
Via Jason Robertshaw
Chirality is an interesting concept. The best way to explain it quickly is an analogy to being left-handed or right-handed. Molecules don't have hands, but they do have an inherent orientation that can be compared to having a dominant hand that you do most of your work with. Sugars are mostly right-handed. Amino acids: Left-handed.
But here's where things get weird: It doesn't have to be that way. In fact, given the randomness and chance through which evolution works, it would make more sense for there to be a lot more diversity in orientation.
All of this backstory is important so that I can tell you about the most hilarious non sequitur I've encountered in 2012.
Chemist Ronald Breslow has a new paper out in the Journal of the American Chemical Society, where he talks about why chirality might be the way it is. For the most part, his ideas are not unreasonable ones. Breslow thinks that life on Earth—and we're talking about life in its simplest forms, like molecules, not actual creatures—could have been "seeded" by material that fell to the planet on an asteroid. The idea is that, if the building blocks of life came from one place—a meteor fall—rather than arising and adapting here, it could explain why there's not the diversity of molecular "handedness" that we might otherwise expect to see.
In fact, in related news, there's another paper out suggesting that Earth could have paid that gift of life forward, with potentially microbe-and-molecule-laden rocks from here traveling far into interstellar space.
What makes Breslow's paper unique is the odd, brief, speculative tangent he gets into at the very end, a tangent which lead to me receiving a press release titled, "Could Advanced Dinosaurs Rule Other Planets?"
An implication from this work is that elsewhere in the universe there could be life forms based on D amino acids and L sugars, depending on the chirality of circular polarized light in that sector of the universe or whatever other process operated to favor the L α‐methyl amino acids in the meteorites that have landed on Earth. Such life forms could well be advanced versions of dinosaurs, if mammals did not have the good fortune to have the dinosaurs wiped out by an asteroidal collision, as on Earth. We would be better off not meeting them.
I suppose it's rather hard to argue with the basic thesis that we'd be better off not meeting a hyper-intelligent T. Rex. But at Dinosaur Tracking, Brian Switek attempts to explain why it's maybe not a great idea for chemists to randomly start pontificating on paleontology. In particular, the "rule" of the dinosaurs was not inevitable and was not dependent on the outcome of a single asteroid collision.
Prior to 250 million years ago, the synapsids—our ancestors and relatives—were the dominant creatures on land. But the apocalyptic extinction at the end of the Permian Period eliminated most synapsid lineages, in addition to many other forms of life. This clearing of the ecological slate is what allowed a different group of creatures to proliferate. Early archosaurs, or “ruling reptiles,” included the archaic forerunners of crocodiles, pterosaurs and dinosaurs, in addition to various groups now extinct, and these creatures dominated the Triassic.
Despite what has been traditionally told, though, the dinosaurian branch of the greater archosaur family tree didn’t immediately out-compete its neighbors. Eoraptor and Herrerasaurus were not the Triassic terrors they were cast as during the mid-1990s. For the most part, Triassic dinosaurs were small, rare, marginal parts of the ecosystems they inhabited. It was only after another mass extinction at the end of the Triassic, around 200 million years ago, that the competitors of early dinosaurs were removed and the reign of the dinosaurs truly began.
Kepler-22b is a newly confirmed exoplanet, orbiting a Sun-like star 600 light years away from Earth. The exoplanet sits in the "habitable zone"—a range of orbits around a star that are, based on what we know about life on Earth, most likely to provide the right conditions for life to happen.
That is pretty damn cool. But it does not mean there must be life on Kepler-22b. As Phil Plait explains on the Bad Astronomy blog, there's a lot we don't know about this exoplanet yet, and "within the habitable zone" is not a guarantee of habitability. Case in point: Our solar system. Earth is within the Sun's habitable zone. But so are Mars and Venus, and you may have noticed that they are not especially teeming with life.
Kepler detects planets when they transit their star, passing directly in front of the star, blocking its light a little bit. The bigger the planet, the more light it blocks. The astronomers going over the data determined that Kepler-22b is about 2.4 times bigger than the Earth. The problem is, that and its distance from its star are all we know. We don’t know if it’s a rocky world, a gaseous one, or what. It may not even have an atmosphere!
Another good post to read on this subject is Matthew Francis' explanation of "habitability" on the Galileo's Pendulum blog. Even the statement, "Kepler 22-b is within the habitable zone," comes along with a lot of assumptions that may or may not turn out to be true.
The following factors are needed to calculate whether a planet is in the habitable zone: The temperature of the host star: the hotter the star, the more it emits light of all wavelengths ... The size of the host star: a large star emits more light from its surface simply because there is more surface area ... The albedo of the planet: how much light gets reflected back into space ... Hand in hand with albedo comes the composition of the planet’s atmosphere—if it has one.
When we say Kepler-22b is in the habitable zone, we're assuming that it has the same atmospheric composition and albedo as Earth. We don't know that. And it's a big leap, bearing in mind (again) that there's not even another planet in our own solar system that shares those characteristics.
I swear, I'm not a fun-hater. Kepler-22b is awesome. Just keep it in context and know that there's still a lot we don't know about this thing.
Size comparison of Kepler-22b via Galileo's Pendulum.