Tag: exobiology

Mars Biosafety

It’s looking more and more likely that Mars might already be inhabited—by Martians. Very tiny ones. Conley’s office serves to prevent NASA from doing to Martians what European explorers did to Native Americans with smallpox. Because Mars lacks Earth’s history of abundant life, it has that much more raw material for Earth’s bacterial stowaways to devour—should any of them, say, come into contact with water, find a niche they can survive in, and start to reproduce. “The whole planet is a dinner plate for these organisms. They will eat Mars.”

Galaxy-size creature?

One could, in principle, imagine “creatures” that are far larger. If we draw on Landauer’s principle describing the minimum energy for computation, and if we assume that the energy resources of an ultra-massive, ultra-slothful, multi-cellular organism are devoted only to slowly reproducing its cells, we find that problems of mechanical support outstrip heat transport as the ultimate limiting factor to growth. At these scales, though, it becomes unclear what such a creature would do, or how it might have evolved.

SETI lower bound

we show that we can set a firm lower bound on the probability that 1 or more additional technological species have evolved anywhere and at any time in the history of the observable Universe. We find that as long as the probability that a habitable zone planet develops a technological species is larger than ~$10^{-24}$, then humanity is not the only time technological intelligence has evolved.

Cold life

fun interdisciplinary work:

Cornell chemical engineers and astronomers offer a template for life that could thrive in a harsh, cold world – specifically Titan, the giant moon of Saturn. Their theorized cell membrane, composed of small organic nitrogen compounds and capable of functioning in liquid methane temperatures of 292 degrees below zero

2022-12-02: The cosmic significance of life on Titan

Saturn’s largest moon, Titan, has a surface temperature of 94 degrees Kelvin above absolute zero, about a third of Earth’s. Titan is located 9.5x farther than the Earth-Sun separation and the surface temperature of Solar system objects declines roughly as the square-root of their distance from the Sun.

Coincidentally, 94 degrees was the temperature of the cosmic microwave background 100ma after the Big Bang when the first generation of stars formed. An object like Titan forming out of gas enriched by heavy elements from the first supernovae, would have had this surface temperature irrespective of its distance from a star. The bath of cosmic radiation would have kept the object warm for 10s of millions of years, sufficiently long for primitive forms of life to emerge on it.

This coincidence of temperatures raises the fascinating possibility of testing how early life could have arisen in the Universe by studying Titan. The question of whether Titan hosts life has cosmic implications. It could unravel the roots of Life in the Cosmos

Venus

This video makes it look like Venus is much closer to the sun than it actually is (100M km) but still, well done.

2014-07-02: Colonizing Venus

If the thought of Thanksgiving Dinner on Venus gives you the heebie jeebies, you don’t even need to think about plunging into the roiling atmosphere with nothing but a cheap plastic heat shield and a thin balloon to save you from the crematorium that yawns down below. Dangle the bird into the depths of the Stygian hell, feast as someone who walks between worlds and lives on an airship that rides the hell born winds 48km above a surface so hot it glows visibly red.

2014-07-03: Venus is a good fraction of solid surface in the solar system.

2020-09-18: Phosphine on Venus

observations indicate a level of phosphine at 20 parts per billion. That may sound low, but it turns out that from what we currently know, on Venus it’s hard to make anywhere near that much. The phosphine was seen at altitudes of at least 50 km. The environment there is pretty hostile to phosphine, which would decompose fairly rapidly. They estimate that that it should all be gone in less than 1 ka at that level, and probably much faster. So something must be actively making it to keep the levels up. But what?

2021-01-14: Jupiter killed Venus?

we present the results of a study that explores the effect of Jupiter’s location on the orbital parameters of Venus and subsequent potential water-loss scenarios. We argue that these eccentricity variations for the young Venus may have accelerated the atmospheric evolution of Venus toward the inevitable collapse of the atmosphere into a runaway greenhouse state. The presence of giant planets in exoplanetary systems may likewise increase the expected rate of Venus analogs in those systems.

DNA precursors in space

Consider this: we have the capability to detect the presence of very specific molecules from 25k light years away. This is just mind-boggling.

Researchers have discovered prebiotic (pre-life) molecules in interstellar space that may have formed on dusty ice grains floating between the stars. The molecules were detected near the center of our Milky Way Galaxy — specifically, the star-forming region Sagittarius(Sgr) B2(N), which is the richest interstellar chemical environment currently known. 1 of the newly-discovered molecules, called E-cyanomethanimine (E-HNCHCN) is one step in the process that chemists believe produces adenine, 1 of the 4 nucleobases of DNA. The other molecule, called ethanamine, is thought to play a role in forming alanine, 1 of the 20 amino acids in the genetic code.

2014-10-03: Isopropyl cyanide, needed for life

Astronomers have detected radio waves within a giant gas cloud in interstellar space corresponding to an unusual carbon-based molecule called isopropyl cyanide, needed for life. Organic molecules usually found in these star-forming regions consist of a single “backbone” of carbon atoms arranged in a straight chain. But the carbon structure of isopropyl cyanide branches off, making this the first interstellar detection of such a molecule


2014-12-02: DNA itself can also survive in space. This makes Panspermia (and contamination of the seas of europa by humanity’s probes) more likely.

Surviving space flight, 1000°C temperatures, re-entry into Earth’s atmosphere, and landing, 35% of the DNA retained its full biological function

2022-03-13: Peptides can form on cosmic dust

Without any of the enzymes that biochemistry provides, the production of peptides is an inefficient 2-step process that involves first making amino acids and then removing water as the amino acids link up into chains in a process called polymerization. Both steps have a high energy barrier, so they occur only if large amounts of energy are available to help kick-start the reaction.

Because of these requirements, most theories about the origin of proteins have either centered on scenarios in extreme environments, such as near hydrothermal vents on the ocean floor, or assumed the presence of molecules like RNA with catalytic properties that could lower the energy barrier enough to push the reactions forward. And even under those circumstances, “special conditions” would be needed to concentrate the amino acids enough for polymerization. Though there have been many proposals, it isn’t clear how and where those conditions could have arisen on the primordial Earth.

But now a group of astrobiologists showed that peptides, the molecular subunits of proteins, can spontaneously form on the solid, frozen particles of cosmic dust drifting through the universe. Those peptides could in theory have traveled inside comets and meteorites to the young Earth — and to other worlds — to become some of the starting materials for life.

DNA sequencing on Mars

venter is such a show off. after wining the human genome race, he sailed around the world, collecting dna samples, and doubled the number of all known genes. then he claimed to have created “synthetic life”, and now this. the man clearly has enormous talent, but i wonder if he is as insufferable as the biography suggests.

Craig Venter and Jonathan Rothberg are competing to put a DNA sequencing machine on Mars, each claiming that it is the best way to search for and confirm Marian life. “This will work only if the DNA on Mars is exactly the same in its fundamental structure as on Earth. It is very unlikely that terran DNA is the only structure able to support Darwinian evolution.” Though I lean slightly toward Venter. Some of the chemistry of DNA life has been shown to imply have the best combinations of stability and just the right breakability and attachment probabilities in the bonds.

White Dwarf Habitable Zones

Planet hunters may be missing a trick. White dwarfs could be good targets for exoplanet searches. They are as common as Sun-like stars, the most common ones have a surface temperature of 5000 K and this should produce a habitable zone at distances of 0.01 AU for periods in excess of 3 ga. That’s long enough for something interesting to have emerged on these bodies.

my drake equation estimate just went up