Great Balls of ‘Space Mud’ May Have Built Earth and Delivered Life’s Ingredients

space-mud
Artist’s impression of the molten surface of early Earth (NASA)

When imagining how our planet formed 4.6 billion years ago from the protoplanetary disk surrounding our sun, images of large pieces of marauding space rock slamming into the molten surface of our proto-Earth likely come to mind.

But this conventional model of planetary creation may be missing a small, yet significant, detail. Those massive space rocks may not have been the conventional solid asteroids — they might have been massive balls of space mud.

This strange detail of planetary evolution is described in a new study published in the American Association for the Advancement of Science (AAAS) journal Science Advances and it kinda makes logical sense.

Using the wonderfully-named Mars and Asteroids Global Hydrology Numerical Model (or “MAGHNUM”), planetary scientists Phil Bland (Cornell University) and Bryan Travis (Planetary Science Institute) simulated the movement of material inside primordial carbonaceous chondrite asteroids — i.e. the earliest asteroids that formed from the sun’s protoplanetary disk that eventually went on to become the building blocks for Earth.

space-mud1.jpg
A simulated cross section of a 200-meter wide asteroid showing its internal temperature profile and convection currents (temperatures in Celsius). Credit: PSI

It turns out that these first asteroids weren’t cold and solid lumps of rock at all. By simulating the distribution of rock grains inside these asteroids, the researchers realized that the internal heat of the objects would have melted the icy volatiles inside, which then mixed with the fine dust particles. Convection would have then dominated a large portion of these asteroids, causing continuous mixing of water and dust. Like a child squishing a puddle of dirt to create sloppy “mud pies,” this convection would have formed a ball of, you guessed it, space mud.

Travis points out that “these bodies would have accreted as a high-porosity aggregate of igneous clasts and fine-grained primordial dust, with ice filling much of the pore space. Mud would have formed when the ice melted from heat released from decay of radioactive isotopes, and the resulting water mixed with fine-grained dust.”

In other words: balls of mud held together by mutual gravity, gently convected by the heat produced by the natural decay of radioactive materials.

Should this model hold up to further scrutiny, it has obvious implications for the genesis of life on Earth and could impact the study of exoplanets and their habitable potential. The ingredients for life on Earth originated in the primordial protoplanetary soup, but until now the assumption has been that the space rocks carrying water and other chemicals were solid and frozen. If they were in fact churning away in space as dynamic mud asteroids, they could have been the “pressure cookers” that delivered those ingredients to Earth’s surface.

So the next question would be: how did these exotic asteroids shape life on Earth?

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Enceladus Could Be a Cosmic Shaker for the Cocktail of Life

NASA/JPL-Caltech/Space Science Institute

A little frozen Saturn moon, with a diameter that could easily fit inside the state of New Mexico, holds some big promises for the possibility of finding basic alien life in our solar system.

Enceladus is often overshadowed by its larger distant cousin, Europa, which orbits Jupiter and the Jovian moon’s awesome potential has been widely publicized. But Enceladus has one thing Europa doesn’t — it has been visited very closely by a robotic space probe that could take a sniff of its famous water vapor plumes. And this week, there was much excitement about another facet of the moon’s complex subsurface chemistry, thanks to analysis carried out on data gathered by NASA’s Cassini mission.

But before we get into why this new discovery is so cool, let’s take a very quick look at the other signs of Enceladus’ life-giving potential.

The Cocktail Of Life

Being living, breathing creatures on a habitable planet, it may not come as a surprise to you that for biology to evolve, it needs a few basic ingredients. Liquid water is a definite requirement, of course. Heat also helps. Throw some organic chemistry into the mix and we have a party.

Enceladus, however, is a tiny icy globe, there’s no sign of liquid water on its surface. But when Cassini arrived at Saturn in 2004, Enceladus revealed some of its best-kept secrets. Firstly, it may be a smooth ice ball, but the moon has a large quantity of water under its surface. This water even escapes as geysers, through fissures in its icy crust, producing stunning plumes that eject material hundreds of miles high and into Saturn’s rings.

Before Cassini was launched to Saturn, we had little clue about Enceladus’ watery potential — though this finding explained why Enceladus appeared so bright and how it contributes material to Saturn’s E-ring. Fortunately, the spacecraft has an instrument on board — a mass spectrometer — that could be used to “taste” the watery goodness of these plumes. During its Enceladus flybys, Cassini was able to fly through the plumes, revealing a surprisingly rich chemical cocktail — including a high concentration of organic chemistry.

It’s as if all the building blocks of life have been thrown into a small icy cocoon, shaken up and gently heated from within.

Now, another fascinating discovery has been made. Further analysis of Cassini data from its last 2015 plume fly-through, molecular hydrogen has been detected and planetary scientists are more than a little excited to add this to Enceladus’ habitable repertoire.

Deep In The Enceladus Abyss

“Hydrogen is a source of chemical energy for microbes that live in the Earth’s oceans near hydrothermal vents,” said Hunter Waite, principal investigator of Cassini’s Ion Neutral Mass Spectrometer (INMS) at the Southwest Research Institute (SwRI), in a statement on Thursday (April 13). “Our results indicate the same chemical energy source is present in the ocean of Enceladus.”

This hydrogen could be a byproduct of chemical reactions going on between the moon’s rocky core and the warm water surrounding it. And there’s a lot of hydrogen gas being vented, probably enough to sustain basic lifeforms deep in the Enceladus abyss.

“The amount of molecular hydrogen we detected is high enough to support microbes similar to those that live near hydrothermal vents on Earth,” added co-author Christopher Glein, who specializes in extraterrestrial chemical oceanography, also of SwRI. “If similar organisms are present in Enceladus, they could ‘burn’ the hydrogen to obtain energy for chemosynthesis, which could conceivably serve as a foundation for a larger ecosystem.”

Yes, we’re talking alien microbes. (Also, “extraterrestrial chemical oceanography” — oceans on other worlds! — is one hell of a mind-blowing topic to specialize in, just sayin’.) And did he mention “larger ecosystem”? Why yes! Yes he did.

So, in short, we know Enceladus has a liquid water ocean. We know that it has an internal heat source (hence the liquid oceans). We also know there’s organic chemistry. And now there’s solid hints that there’s water-rock interactions going on that terrestrial microbes living at Earth’s ocean vents like to munch on. If that’s not a huge, blinking neon sign pointing at Enceladus, saying: “We need a surface mission here!” I don’t know what is.

Although the researchers are keen to emphasize that alien microbes have not been found (because Cassini isn’t capable of looking for life), the universe has given us a moon-sized Petri dish where an “ecosystem” may have taken hold. All the ingredients are there, wouldn’t it be cool to find out if Enceladus could be another place in the solar system where life may be hanging out?

There was also some great news about Europa’s habitable potential this week, but you can go here for that piece of cosmic awesomeness.

Want to know more about Cassini’s final months at Saturn, check out my recent Space.com article on the commencement of the veteran mission’s Grand Finale.

Astroengine Gets Quoted in National Geographic

The December 2010 edition of National Geographic
The December 2010 edition of National Geographic

A couple of months ago I was contacted by National Geographic magazine notifying me that one of their writers had quoted me in an article for their December issue. Pretty cool, I thought. But then I forgot all about it.

Then, I received a note from the ever watchful Bill Hudson (@2012hoax) telling me Astroengine had been printed on page 99. I quickly scurried over to the National Geographic website to find, sure enough, I was there too: on page 3 of the online article “Star Struck.”

The following morning, I received a complementary copy of the December edition so I could see Astroengine in print for the first time.

National Geographic’s special feature takes a fascinating tour of the Milky Way and when discussing metal-poor stars in the outermost reaches of our galaxy, the article quotes the title of the Astroengine post “Life is Grim on the Galactic Rim.” Obviously they like my rhyming skills.

Thank you National Geographic!

I’ve been told I can write a blog with an excerpt from the superb article written by Ken Croswell, so that’ll be coming right up!

I think I need to blog more…

Dead On Arrival: Necropanspermia Spawned Life on Earth?

Are those Martian fossils in meteorite ALH84001? (NASA)
Are those Martian fossils in meteorite ALH84001? (NASA)

Panspermia” is a hypothesis that life is transferred from planet-to-planet and star system-to-star system through some interplanetary or interstellar means.

But for panspermia to work, this life needs to be sufficiently protected — and, um, kept alive — from the worst the universe can throw at it (such as radiation, cold and vacuum). Alas, when considering interstellar hops, the timescales are likely too long (i.e. millions of years) and said life will be dead on arrival.

We know that Earth Brand™ life is a pretty hardy thing. After all, we’ve tortured terrestrial microbes and mosquito larvae in the vacuum of space to see if they’d pop. Sure enough, when brought back to terra firma the various creatures wriggled and squirmed as if nothing had happened. But these experiments in orbit were carried out over the course of months or years. While this might be suitable for interplanetary transfers, it would take millions of years for an extraterrestrial interloper to traverse even a modest interstellar gap.

Any hitchhikers that were alive on a stellar wind-blown particle will be toast (or, more accurately: freeze-dried, pulverized, mashed-up, DNA-shredded mess) on reaching their exotic destination eons later.

What good are tiny alien fossils when the panspermia model is supposed to seed other worlds with life… that’s actually alive?

Enter a new incarnation of pansermia: “Necropanspermia.”

Conceived by Paul Wesson, of Herzberg Institute of Astrophysics in Canada, necropanspermia is the transfer of the information of life to new worlds, wriggling extraterrestrial bacterium not required.

Assuming alien microbial life has made the trip across interstellar space, died and then fossilized, Wesson reckons the information contained within the long-dead microbe could be used as some kind of template by a hospitable world to use and grow new life. (It’s not quite zombie science, but it’s hard not to say “reanimated alien corpse.”)

Wesson even goes so far to suggest ET’s microbial remains can be “resurrected.”

“Resurrection may, however, be possible.” Wesson concludes in his Space Science Reviews paper. “Certain micro-organisms possess remarkably effective enzyme systems that can repair a multitude of strand breaks.”

Hypothesizing about various forms of panspermia may seem more like a philosophical argument, but Wesson suggests that we might be able to find evidence for necropanspermia if we collect some dust samples from the outermost reaches of the solar system, far enough away from Earth’s biological pollution.

Alas, as the Hayabusa asteroid mission has proven, capturing dust from anywhere in space isn’t easy.

Read more about necropanspermia in my Discovery News article “Life on Earth Spawned by Dead Alien Microbes?

Ingredients for Life on Gliese 581g?

Credit: Lynette Cook

Just in case you haven’t heard, astronomers have released news about an “Earth-like” exoplanet orbiting within the “Goldilocks zone” of a star some 20 light-years away. This is awesome, but does it mean Gliese 581g is habitable? Does it mean life is already slithering across its surface?

Judging by an exuberant claim by Steven Vogt, professor of astronomy and astrophysics at University of California Santa Cruz, one would think we now know there’s life on this strangely familiar world.

“Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say that the chances for life on this planet are 100 percent. I have almost no doubt about it,” Vogt told Discovery News when the announcement broke on Wednesday.

100%?

Why did he say that his personal view was that the chances for life on Gliese 581g are 100%? At first glance, it is easy to see where he’s coming from.

Goldilocks Zone

Firstly, the exoplanet orbits close to a small red dwarf star (called Gliese 581), with a fast-paced orbit of 37 days. This is important as the energy output of a red dwarf is tiny when compared to our Sun (which is a yellow dwarf star, in case you were wondering) — to receive an equivalent amount of heating as the Earth, Gliese 581g needs to be much closer to its star.

Also, it isn’t orbiting too close. It is within the habitable zone (or the “Goldilocks zone,” i.e., a zone that’s not too hot or too cold) of the system. Therefore there’s a high probability that if water is present on its surface, it’s likely to be in liquid form. The presence of liquid water would be exciting as Earth Brand™ life likes liquid water.

Secondly, Gliese 581g is small for an exoplanet discovered thus far. Weighing in at a minimum mass of 3x that of the Earth, it could certainly have some Earth-like qualities. This has another implication; the world has enough gravitational oomph to hold onto an atmosphere — another ingredient that life seems to like (assuming it’s not of the bone-crushing, lead-boiling, Venus-type atmosphere).

It’s Complicated

But there’s a few complications. To be within the habitable zone of its parent star, Gliese 581g will be “tidally locked.” This means that one side of the exoplanet will always be facing the star. On the far side (or, indeed, the “dark side”) it will be cold whilst the near side will always be hot. Having one perpetual day doesn’t sound very Earth-like to me. But there is an upside to this strange orbit.

“This planet doesn’t have days and nights. Wherever you are on this planet, the sun is in the same position all the time. You have very stable zones where the ecosystem stays the same temperature… basically forever,” Vogt said. “If life can evolve, it’s going to have billions and billions of years to adapt to the surface.”

So a tidally-locked planet could have a stable atmosphere and perhaps life could evolve as a result. What could be considered to be a negative has just become a positive.

With all this good news, why wouldn’t life be thriving on this world?

Unknowns and Assumptions

There’s still a lot of unknowns and assumptions being made. For a start, the presence of Gliese 581g was detected by measuring the “wobble” of the star as the exoplanet orbits (its gravity tugs on the star as it circles). Therefore its mass and orbital radius can be derived. But we have no information about its atmosphere; the world doesn’t pass in front (or “transit”) the star from our perspective, so we can’t get a peek into its atmosphere.

Therefore we have zero clue as to whether it even has an atmosphere. It might not have an atmosphere, but then again it could have a very thick atmosphere — two extremes that would would put a stop to any Earth Brand™ life evolving. Also, we have zero clue if there’s any water there, it’s just guesswork that suggests there might be. There’s also the huge unknown as to whether life is ubiquitous in the cosmos or not.

Bread in the Oven

It’s a bit like baking a loaf of bread when you have all the necessary ingredients to make bread, but you have no clue about what quantities to use. Gliese 581g appears to have most of the ingredients for life (and with a few assumptions, it has all the ingredients for life), but we only have a general idea as to what quantities these ingredients come in.

If you threw flour, water and yeast straight into the breadmaker in random quantities, would you get a loaf of bread? What if you forgot to add the yeast?

Gliese 581g is that breadmaker. Unfortunately we have no clue if it can make bread.

For more on this incredible discovery, read Irene Klotz’s Discovery News article: “Earth-Like Planet Can Sustain Life

Cassini Detects Salt: Enceladus Probably Has a Liquid Ocean

The small icy Saturn moon might have liquid sub-surface oceans after all (NASA)

In October 2008, Cassini flew very close to the surface of Saturn’s icy moon Enceladus. From a distance of only 50 km from the moon, the spacecraft was able to collect samples of a plume of ice. In an earlier “skeet shot”, Cassini captured detailed images of the cracked surface, revealing the source of geysers blasting the water into space. At the time, scientist were able to detect that it was in fact water ice, but little else would be known until the molecular weight of chemicals in the plume could be measured and analysed.

At the European Geophysical Union meeting in Vienna this week, new results from the October Enceladus flyby were presented. Frank Postberg and colleagues from the Max Planck Institute for Nuclear Physics have discovered traces of sodium salts and sodium bicarbonate in the plume for the first time.

It would appear that these chemicals originated in the rocky core of the moon and were leached from the core via liquid water. The water was then transported to the surface where it was ejected, under pressure, into space. Although scientists are aware that the chemical composition in the plume may have originated from an ancient, now frozen, sub-surface ocean, the freezing process would have isolated the salt far from the surface, preventing it from being released.

It is easier to imagine that the salts are present in a liquid ocean below the surface,” said Julie Castillo of NASA’s Jet Propulsion Laboratory in Pasadena, California. “That’s why this detection, if confirmed, is very important.”

This is the best evidence yet that Enceladus does have a liquid ocean, bound to cause a stir amongst planetary scientists and re-ignite excitement for the search for life living in a salty sub-surface ocean.

Source: New Scientist

Ceres: Life? Pluto: Not So Much

The dwarf planet soap opera continues

The dwarf planet Ceres. Fuzzy (NASA/Hubble)
The dwarf planet Ceres. Fuzzy (NASA/Hubble)

Could the dwarf planet Ceres maintain life? Possibly, says a scientist from a German university. According to new research, this ex-asteroid (who did a deal with the IAU to sell out Pluto, trading in its asteroid status to become a dwarf planet, at the expense of Pluto being demoted from being a planet. Obviously) may have harboured microbial life near geothermal vents in hypothetical liquid oceans (I emphasise hypothetical). Not only that, but Ceres’ chilly microbes could have been kicked into space by meteorites, spreading life throughout the Solar System. Forget Mars (you’re looking too hard), forget Europa (a moon? With life? Pah), the new giver of life could be Ceres, the dwarf planet we know next to nothing about.

Then there’s Pluto. Not much chance of life there either (although it would be fun to speculate, there is methane there after all), but the hard-done-by newly-christened dwarf planet has a rather bizarre atmosphere. Its temperature profile is upside down. Oh, and Pluto has just been reunited with its planetary status… in Illinois only (because a governor really does know more about planets than 400 members of the International Astronomical Union).
Continue reading “Ceres: Life? Pluto: Not So Much”

The Search For Life, What’s the Point?

Another mission, another brave “search for life”…

Is it me, or does virtually every robotic foray into space have some ET-searching component attached? In the case of Mars exploration, every lander and rover’s prime directive is find life, evidence of past life, potential for life or the building blocks of life. Even the very first man-made artefact to land (crash) on the planet, the 1971 Soviet Mars 2 mission, was designed to find organic compounds and… any sign of life.

On writing an article yesterday (“Wasteful” Sample Storage Box Removed from Mars Science Laboratory), I started to think that we might just be trying a little too hard and spending too much money on this endeavour. Perhaps there’s another way for us to work out if we are, indeed, an interplanetary (possibly intergalactic?) oasis, or a component of a biological cosmic zoo…
Continue reading “The Search For Life, What’s the Point?”