Are we asteroid dust?
Why does that matter? Well it won't cause traffic jams of people rushing to the bunkers in case the aliens are coming. But it might be giving us a piece of the puzzle of how life began: One promising theory of how life formed is that prebiotic molecules, each having one or two lifelike properties, were bought together by chance and stayed together because their ability to survive was greater that way (religions across the world have much more fun ones, involving life being made of clay, people being made of other peoples ribs, the sky being made from a huge skull, etc. etc.).
For example; lipid molecules can form enclosed cell walls when mixed with water, and these enclosed cell walls will grow and replicate (two things that life does). But they have no means of evolution... unless they joined forces with RNA molecules at some point (which can evolve). Together the two systems were able to spread further, and were more robust, and were able to evolve.
So where did those prebiotic molecules-with-some-lifelike-properties come from? The same place, it seems, that the rocks and water of this world came from: Space.
Above: A simulation, showing planets growing from the rocks and ices in the protoplanetary disk. Courtesy of Michegan University.
Yes, in case you haven't read my ramblings here before: Earth (as far as we know) was formed by the collisions and mergings of countless billions of protoplanets, asteroids and planetismals, in the swirling mass of the Sun's protoplanetary disk. Because there were more radioactive materials around back then even very small worlds had enough energy for things like volcanic activity and (subsurface) liquid water.
Above: A full talk on how tiny worlds in the ancient solar system could have things (like volcanoes and magnetic fields) which only full sized planets can have today. Courtesy of Havard-Smithsonian
So, before Earth ever formed, the primitive organic matter already present in the protoplanetary disk was being changed by these processes into more complex stuff. When these worlds splatted into each other, or got merged into planetary embryos, chunks of them containing the processed organic matter - things like amino acids (which build proteins) and nucleobases (which build RNA and DNA) - were blasted into space and eventually fell onto the young Earth,
Which is where the new study comes in: By looking at various pre-biological organic molecules, from a range of meteorite families, the team from found evidence that some of the parent worlds shared the same chemical reactions, and some of them had different reactions going on. This meant that some of these early worlds were making mainly DNA building blocks, and some were making more protein building blocks (or sugars, or something else).
It all adds to the picture that the ancient solar system had many, many worlds, each with their different character. And the origin of life is tied up in what happened on these worlds, long before the Sun ever rose on early Earth.
Elsewhere in the Universe:
For a long time it's been an unresolved question: where did Earth's water come from? Recently evidence from the Rosetta space probe, which is exploring comet 67-P, suggested that Comets were a less likeyl source of water. As the Earth itself formed from asteroids an comets this made water bearing asteroids a more likely source, and now observations of an asteroid impacting a white dwarf (a dead and fading star) have provided evidence that water bearing asteroids may be common in other solar systems too.
Most planetary geologists are pretty convinced that there's a sea beneath the ice of the south pole of Enceladus. But that's a different kettle of fish from that ocean having the chemical ingredients neede for life. We know there are signs of organic molecules in the material being vented from the ocean into space, but is there a chemical power source for living organisms? New evidence suggests that there is: A process called serpentization may be able to set up the energy gradients needed.
Scuttlebutt on the interweb is that there's a renewed push for the Europa Clipper mission to get a lander. A lander portion of the mission would enhance the chances discovering life there, and, as U.S. Rep John Culberson, who oversees NASA's budget, said "Why go there and not answer the most important question?"
Although the MESSENGER space probe to Mercury has been slammed into the rock of that planet at 8000 km/hour (space exploration allows you to throw out the trash in a way that would demolish the town) the data it has sent back will be picked over for many years to come. One result that has cropped up recently is that the magnetic field of Mercury may predate even Earths.
Curiosity sends back stunning picture of the Martian sunset:
|Above: On Earth the sky is blue and the sunset orange. On Marsv the sky is orange and the sunset is blue. Why? Because if the skys and sunsets were the same the hoax theorists would never, ever, shut up. Courtesy of NASA|
Elsewhere on the internet: