Mars had an ocean: billions of years ago. Scientists are piecing together the story of how Mars became the world it is now: and trying to figure out where Martian methane comes from.
Other scientists have discovered another reason to look for life on planets orbiting red dwarf stars: and there's the ongoing discussion of how to define "life."
We're learning more about this universe, and discovering that there's much more to learn.
- Exoplanet Discoveries: 2014
- Martian Methane, and More
- Defining "Life"
- Time, Tides, and Looking for Life
I'm not sure why some folks associate 'being religious' with moping around, brooding on the futility of it all and how everybody should act as if their pet canary died.
I understand feeling tired, guilty, and dragging through the day. Decades of undiagnosed major depression saw to that, and that's another topic. (October 5, 2014)
But we live in a universe filled with wonders: a beautiful, ordered cosmos; unfolding in accord with physical laws which we are beginning to understand. (Catechism of the Catholic Church, 32)
No matter where we look, we can see "wonderful things." The trick is learning to notice them. (June 27, 2014)
Being curious, studying the universe, is part of being human. Science and technology aren't transgressions: they're tools that we're expected to use wisely. (Catechism, 35-36, 301, 303-306, 311, 1704, 2293-2296)
I've said this before, a lot.
Thinking is not a sin. It's faith and reason. We are rational creatures, and expected to use our brains. ("Fides et Ratio," John Paul II (September 14, 1998); Catechism of the Catholic Church, 35, 32, 154-159, 299)
(From David A. Aguilar (CfA), via Space.com, used w/o permission.)
("Artist's concept of the exoplanet Kepler-10c, the 'Godzilla of Earths' that's 17 times more massive than Earth. The planet and its lava-world sibling Kepler 10b (background) orbit the star Kepler-10 about 560 light-years from Earth."
"The Biggest Alien Planet Discoveries of 2014"As usual with these 'best of' lists, Space.com's Mike Wall picked 10 of 2014's exoplanet discovery events. I've added links to more-or-less relevant Wikipedia articles:
Mike Wall, Space.com (December 29, 2014)
" This past year was a banner one for the field of exoplanet science, with the tally of known alien worlds doubling to nearly 2,000 by the end of 2014.
"Here's a look at the top exoplanet discoveries of 2014, from the first potentially habitable Earth-size world to a staggering haul of 715 newly announced alien planets..."
- 'Earth's cousin'
- A habitable world next door?
- 715 newfound exoplanets
- 'The Godzilla of Earths'
- Gas dwarfs
Also called mini-Neptunes
- The first exomoon?
- Or maybe a rogue planet
- The first exoplanet of Kepler's new mission
- The oldest potentially habitable alien planet
- Planets around every star?
About one in five have Sun-like (class G) stars at least one roughly Earth-size planet
- Earth-like worlds in two-star systems? OGLE-2005-BLG-390Lb
I wrote about Kepler-186f twice this year. The planet's diameter is 1.1 times Earth's: and it might be made of roughly the same stuff. Kepler 186f and other pretty-close matches to Earth orbiting red dwarf stars is focusing attention on these slow-burning suns. (May 9, 2014; April 25, 2014)
"Habitable" doesn't mean "inhabited," though. We still don't know whether there's life on billions of worlds: or just on Earth. Then there's the question of what "life" is, and I'll get back to that.
(From NASA/JPL-Caltech/MSSS, used w/o permission.)
("The first definitive detection of Martian organic chemicals in material on the surface of Mars came from analysis by NASA's Curiosity Mars rover of sample powder from this mudstone target, 'Cumberland.' "
"NASA Rover Finds Active and Ancient Organic Chemistry on Mars"Like I've said before, "organic" doesn't mean "living."
Jet Propulsion Laboratory/NASA (December 16, 2014)
"NASA's Mars Curiosity rover has measured a tenfold spike in methane, an organic chemical, in the atmosphere around it and detected other organic molecules in a rock-powder sample collected by the robotic laboratory's drill.
" 'This temporary increase in methane -- sharply up and then back down -- tells us there must be some relatively localized source,' said Sushil Atreya of the University of Michigan, Ann Arbor, a member of the Curiosity rover science team. 'There are many possible sources, biological or non-biological, such as interaction of water and rock.'
"Researchers used Curiosity's onboard Sample Analysis at Mars (SAM) laboratory a dozen times in a 20-month period to sniff methane in the atmosphere. During two of those months, in late 2013 and early 2014, four measurements averaged seven parts per billion. Before and after that, readings averaged only one-tenth that level...."
Methane is "organic" in the sense that it contains carbon: and isn't a carbide, carbonate, or another of the short list of carbon-containing substances that we don't call "organic."
What's "organic" and what's not is a tad arbitrary: dating from the days when natural philosophers thought organic substances contained a life-force.
Vitalism made sense until we learned more about atoms, and that's yet another topic. Topics. I've discussed phlogiston, quantum field entanglement, and getting a grip before.
Curiosity found organic chemicals in powder it drilled from "Cumberland," the rock in that picture. This was the first definite detection of organics the Martian surface. The substances may have formed on Mars, or arrived in a meteorite. Either way, we still don't know whether or not Mars supported — or supports — life.
The big deal in this news is that now we have evidence that Mars is chemically active, and has the chemicals needed for life. Whether or not life every got started there: that's another question.
(From NASA/JPL-Caltech/SAM-GSFC/Univ. of Michigan, used w/o permission.)
("This illustration portrays possible ways methane might be added to Mars' atmosphere (sources) and removed from the atmosphere (sinks)."
Figuring out just what the Martian organic chemicals are is complicated. Martian rocks and soil contains perchlorate minerals: molecules containing chlorine and oxygen. Perchlorates are none too healthy for us, but more that 40 microorganisms can grow in the stuff.
The problem scientists have with Martian soil and rock samples is that perchlorates react with the other chemicals they're trying to analyze. Sorting out what a sample was before oxygen and chlorine atoms started doing their thing is tricky.
The freshwater lake in Gale Crater dried up billions of years back: But some of its water is chemically bound in rocks that Curiosity has been sampling. Measuring the ratio of deuterium, a comparatively heavy hydrogen isotope, to normal hydrogen in rock samples gives scientists a look at what happened to Martian water:
"...The ratio that Curiosity found in the Cumberland sample is about one-half the ratio in water vapor in today's Martian atmosphere, suggesting much of the planet's water loss occurred since that rock formed. However, the measured ratio is about three times higher than the ratio in the original water supply of Mars, based on the assumption that supply had a ratio similar to that measured in Earth's oceans. This suggests much of Mars' original water was lost before the rock formed...."It looks like a Martian ocean was drying up between 4,000,000,000 and 3,500,000,000 years ago.
We might find traces of microbes that grew when Mars was a bit more hospitable than it is today; but Percival Lowell's imagined Martian civilization, desperately struggling to survive on a dying world, isn't there.
I remember the mix of excitement and disappointment, when Mariner 4 sent back pictures of a cratered Mars: with no trace of canals. Then probes started sending back pictures of Valles Marineris, and the valley networks of the Martian southern highlands: and that's yet again another topic.
- "Mars Methane Detection and Variability at Gale Crater"
(December 16 2014)
- "The Imprint of Atmospheric Evolution in the D/H or Hesperian Clay Minerals on Mars"
(December 16 2014)
(From NASA Ames Imaging Library System (AILS), via Astrobiology Magazine, used w/o permission.)
("Dr Chris McKay and Monika Kress, Professor of Astronomy at San Jose State University on a Spaceward Bound event in the Mojave Deser, CA."
"What is life? It's a Tricky, Often Confusing Question."A key word in that last paragraph is independent origin of life.
Dr. Chris McKay, Astrobiology Magazine (September 18, 2014)
"What is life? This is a question that is often asked and typically confused.
"The confusion starts from the several uses of the word 'life' in English. There are at least three usages as exemplified by the following questions:
"1) Is there life on Mars?
"2) Is there life in this organism?
"3) Is life worth living?
"The definition of 'life' in these three usages is quite different. In the first case, life refers to a collective phenomenon, in the second case it refers to the ability of an individual organism to metabolize and grow, and in the third case life refers to the history of activities that an organism undertakes. The first two usages are of direct relevance to astrobiology.
"The usual definition of life, as used in the first case, is that it is a system of material entities that can undergo evolution, which implies reproduction, mutation and selection. This is what we are looking for on Mars and on other worlds. We would be most interested if it represented a second genesis, in other words an independent origin of life. It is often pointed out that the definition of life as a system capable of evolution implies that single, isolated individuals not of child-bearing age are not 'life.' This is nonsense and confuses the first and second cases of 'life.'..."
If we found life on Mars, that'd be great. But unless is was very different at the sub-cellular level, there'd be a good chance that the Martian critters are descended from microcritters from Earth: or that life on Earth started on Mars; or elsewhere.
Panspermia, the idea that life spreads through the universe — carried by distributed by meteoroids, asteroids, comets, and assorted debris — isn't a crackpot notion. We've recovered Martian rocks on Earth, and found that microbes could get sealed into 'splash' from impacts, and thrown into space; and found DNA components in meteorites. (February 21, 2014; January 17, 2014; October 18, 2013)
Our DNA contains adenine and guanine: but those chemicals aren't "alive." They're some the stuff life is made of: which gets me back to "what is life?"
Dr. Chris McKay notes that some folks "hold the view that an effective search for life on other worlds requires that we first have a concise, agreed on, definition of life." He doesn't agree.
"...Along this line, it has been suggested that once we understand life we will be able to produce a completely mechanistic and predictive theory of life. The example of water is sometimes used. Water is simply defined as two hydrogens joined with one oxygen. However, life is not a simple substance like water, rather it is a process, more like fire than water. There is no simple definition of fire....""No simple definition of fire?" Fire can be defined as "the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products." (Wikipedia)
(Dr. Chris McKay, Astrobiology Magazine)
That's pretty simple, as definitions go: even so, I think Dr. McKay has a point. "Life" is more nearly similar to fire than water.
I also think he's on the right track, saying that looking for "...life on other worlds can be based on what life does rather that its definition. One of the things that life does is build up large specialized molecules, such as DNA and proteins...."
The Viking lander included a biology experiment: soaking Martian soil in water and seeing what happened. The idea was that if microorganisms were in the soil, they'd perk up and start releasing chemicals. The results were — odd. As I recall, one fellow called it "peculiar chemistry."
Years later, University of Giessen's Joop Houtkooper pointed out that there's not much water on Mars. Giving them so much water all at once might have killed them. I've discussed water, biochemistry, and exploding Martians, before. (May 16, 2014; Apathetic Lemming of the North (March 5, 2009))
Dr. McKay finishes his article by saying that dead critters can still be identified as having been alive, because "...the organism was once alive and is composed of organic molecules that are specific to life...." He identifies those as DNA, ATP (adenosine triphosphate), and proteins.
In a way, defining "life" isn't hard. We can tell if something's alive or not just by looking. For example, I'm alive: but a lump of rock on my desk isn't. Simple, right?
Until we start thinking about exactly how we define the difference between "living" and "not living." Over the millennia, folks have come up with some pretty good definitions. I'll focus on two:
- Living things contain a life-force
- Non-living things don't
- Homeostasis: Regulating and maintaining constant internal conditions
- Organization: Made of one or more cells
- Metabolism: Transforming energy by converting chemicals and energy into cellular components
- Growth: Increasing the size of each internal component
- Adaptation: Changing slowly in response to the environment
- Response to stimuli: Changing quickly in response to the environment
- Reproduction: Producing new individual organisms
On the other hand, we're pretty close to building robots that would be "alive" in that sense: and I've been over that before. (August 15, 2014)
"Vitalism is the doctrine that 'living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things'. Where vitalism explicitly invokes a vital principle, that element is often referred to as the 'vital spark', 'energy' or 'élan vital', which some equate with the soul...."All that's left of vitalism these days are pop-psychology and literary references to the four humors: sanguine, choleric, melanchoolic, and phlegmatic — and movies like Lifeforce, a rousing tale involving Halley's Comet and space vampires.
Then there's alchemy, that gave us much of today's chemical lab equipment and terms like methylated spirits. I've written about the pursuit of truth, cosmic influences, and all that, before. (March 20, 2014)
Vitalism made more sense back when philosophy, religion, and systematic study of nature weren't nearly as distinct from each other as they are now.
One of the reasons that our definitions of what's organic and what's not are so apparently-arbitrary is that today's sciences of physics and chemistry were getting started while vitalism was still taken seriously.
Some chemists pointed out that chemical transformations involving by non-living substances are reversible: but chemical transformations permanently change "organic" matter. They're right, in a way. It's impossible to un-cook an egg.
Then Friedrich Wöhler synthesized urea. That was in 1828. John Scott Haldane (1860-1936) wasn't, strictly speaking, a vitalist: but he wasn't a mechanist, either: and that's still another topic.
I'm a Catholic, so I must believe that natural processes are created by God, that the universe is beautiful, and follows knowable physical laws. (Catechism, 32)
Because physical phenomena reflect some facet of the Creator's truth, according to their nature, we can learn something about God by studying them. (Catechism, 282-289, 306-308)
I also think poetry isn't science, don't consult the Bible when troubleshooting a software glitch: and that's another topic or two, too. (July 18, 2014; January 14, 2011)
(From Rory Barnes, University of Washington; via ScienceDaily, used w/o permission.)
("For certain ancient planets orbiting smaller, older stars, the gravitational influence of an outer companion planet might generate enough energy through tidal heating to keep the closer-in world habitable even when its own internal fires burn out. But what would such a planet look like on its surface? Here, UW astronomer Rory Barnes provides a speculative illustration of a planet in the habitable zone of a star about the size of the sun. 'The star would appear about 10 times larger in the sky than our sun, and the crescent is not a moon but a nearby Saturn-sized planet that maintains the tidal heating,' Barnes notes. 'The sky is mostly dark because cool stars don't emit much blue light, so the atmosphere doesn’t scatter it.' "
"Companion planets can increase old worlds' chance at life"Planetary scientist Richard Greenberg, graduate student Christa Van Laerhoven, and U. of Washington astronomer Rory Barnes ran simulations that showed what happens to Earth-sized planets with non-circular orbits in low-mass stars' habitable zones.
Featured Research, University of Washington, ScienceDaily (August 1, 2014)
"Having a companion in old age is good for people -- and, it turns out, might extend the chance for life on certain Earth-sized planets in the cosmos as well.
"Planets cool as they age. Over time their molten cores solidify and inner heat-generating activity dwindles, becoming less able to keep the world habitable by regulating carbon dioxide to prevent runaway heating or cooling.
"But astronomers at the University of Washington and the University of Arizona have found that for certain planets about the size of our own, the gravitational pull of an outer companion planet could generate enough heat -- through a process called tidal heating -- to effectively prevent that internal cooling, and extend the inner world's chance at hosting life...."
Most of us, when we think of tidal forces at all, think of tides in Earth's ocean. They happen because the gravity of Earth's moon is a trifle stronger on the side or our planet nearest the moon.
Besides pulling water around, the gravitational taffy pull stretches Earth's crust and interior — a little. All that stretching and releasing generates heat. (November 28, 2014; July 18, 2014)
This Earth tide is barely noticeable, partly because there's so much else going on inside our planet.
Over the last few decades, we've learned quite a bit about what's happening inside Earth. I'm pretty sure that scientists will be refining plate tectonics theory for quite a while: but there doesn't seem to be much question about the basics of what's going on in the first few hundred miles below our feet.
(From USGS, via Astrobiology Magazine, used w/o permission.)
("From USGS, An artist's impression showing tectonic activity spurring volcanic eruptions."
Earth's a geologically active place: which apparently helps keep our world habitable. Volcanoes replenish the carbon dioxide that helps regulate temperatures, and important materials get recycled when the oceanic lithosphere sinks back into Earth's interior. (Wikipedia)
It's possible that Earth is just about as small as a planet can be, and still be habitable. (Apathetic Lemming of the North (December 5, 2009))
(From NASA/JPL-Caltech, via Astrobiology Magazine, used w/o permission.)
("An artist's impression of planets encircling a red dwarf star."
"...'When the planet is closer to the star, the gravitational field is stronger and the planet is deformed into an American football shape. When farther from the star, the field is weaker and the planet relaxes into a more spherical shape,' Barnes said. 'This constant flexing causes layers inside the planet to rub against each other, producing frictional heating.'The sort of stars studied are those with less than one-quarter the mass of the Sun. These are the smaller, cooler, red dwarf stars, with surface temperatures around 3,000 Kelvin or lower.
"The outer planet is necessary, Barnes added, to keep the potentially habitable planet's orbit noncircular. When a planet's orbit is circular, the gravitational pull from its host star is constant, so its shape never changes, and there is no tidal heating.
"And so, the researchers conclude, any discoveries of Earth-sized planets in the habitable zone of old, small stars should be followed by searches for outer companion planets that might improve the inner world's chance at hosting life...."
(Featured Research, University of Washington, ScienceDaily)
Red dwarfs 'burn' hydrogen in fusion reactions, combining two hydrogen atoms to produce a helium atom and energy: but they burn slowly.
Scientists figure that red dwarfs will last longer than the universe has been around. That means that no red dwarf has run out of hydrogen yet.
Artists' impressions of red dwarfs often make these stars literally red. I like the pictures: but if we were standing on a red dwarf's planet — the 'sun' would be a cheery orange hue.
Even a star with 7.5% our sun's mass would be 2,300 Kelvin on the parts we see: shedding reddish-orange light on the landscape.
A more everyday comparison: a match flame burns at about 1,700 Kelvin. That graph is a Plankian locus, a fancy word for a chart showing the color of an (ideal) object as it's heated.
It seems to me that we might find habitable planets circling brown dwarfs, not-quite-stars like UGPS J072227.51-054031.2. And that's — almost another topic.
Getting back to that article: it looks like some of most durable surface habitats in the universe may be on planets circling small, dim, stars; with a larger outer companion to keep the inner world's orbit non-circular.
Tidal heating could keep habitable world's tectonics working, recycling material; while the low-mass star kept shining as billions of years pass.
Folks making really long-term plans might decide that places like that are good retirement spots.
- "Ancient Worlds Could Be Kept 'Alive' by Gravitational Nudges"
Adam Hadhazy, Astrobiology Magazine (Adam Hadhazy - June 26, 2014 )
- "Tides, planetary companions, and habitability: habitability in the habitable zone of low-mass stars"
C. Van Laerhoven, R. Barnes, R. Greenberg; Monthly Notices of the Royal Astronomical Society (Received in original form January 22, 2014; April 2, 2014; Accepted April 3, 2014; published online May 12, 2014)
- "Tidal Evolution of a Secularly Interacting Planetary System"
Richard Greenberg, Christa Van Laerhoven; Astrophysical Journal (Submitted September 20, 2010; Revised November 18, 2010; Second revision February 18, 2011; Third revision March 7, 2011; Accepted for publication March 11, 2011)
- "Spotting a Diamond (?) Planet, Searching for Life"
(December 19, 2014)
- " 'Organic,' 'Wow!' — and Double Planets"
(November 28, 2014)
- "Kapteyn b, Habitable Zones, and Using Our Brains"
(July 18, 2014)
- "Habitable Worlds, Homer, and Haldane — or — Ganymede's Oceans, and Imagining Kepler-186f's Sunsets"
(May 9, 2014)
- "The Search for Life: Earth-Size Planet, in the Habitable Zone — Found"
(April 25, 2014)