Something like a loose virus would suffice, but I'm hoping for something more astronomical. I've looked a little into coronal mass ejections and gamma ray bursts, but it seems those would destroy the atmosphere. I want the world to exist in a a state where after it ends, it can still be populated by another species.
An asteroid impact would do the trick. A few number of smaller species would be able to survive and adapt after the impact.
I'd go with super volcano. Except you'd be looking at hundreds of thousands of years before species started evolving.
Airborn HIV would be a potential if you wanted to go down the vitus route. Astronomically, an asteroid or meteorite would probably be the best bet, though a huge dust cloud would cause extensive climate change, which I'm not sure is what you mean by "intact". You could always have an extra-terestrial virus being delivered by a meteorite, sort of a la The Andromeda Strain. Another option would be a neutron bomb, which would only affect biological material, though I'm not sure how easy that would be to work into your plot.
A large enough matter-antimatter explosion well above the Earth's atmosphere would sterilize the planet with gamma radiation. You might need several such explosions to sterilize the entire surface, because the planet itself would absorb a lot of the radiation, so life could remain on the far side. Some organisms might still survive the irradiation, but the disruption of the ecosystem would probably kill most of the them. Your planet would be as nearly lifeless as a viable world for life to develop can possibly become. The explosions would probably have to be the result of a mutually assured destruction scenario.
What kind of cataclysm are we talking here? Are the plants still around? Animals? Sea life? Bacteria? Micro-organisms that survive deep in the earth's core? There's a huge amount of variation between different apocalypses. Some say that humans dying out would qualify, others would say that every strain of life would have to be eradicated. What are you aiming for?
Improbable at those temperatures and pressures. In any event, it would not be carbon-based life as we know it. The more specific you get, the lower the probability of total extinction. For example, a virus that selectively kills humans is bound to leave survivors. Some would escape infection, and some would likely have a natural resistance/immunity.
I'm looking for something that could wipe out all life on a planet, but allow an outsider such as an astronaut to return days later, land, and realize everybody is dead.
All life? In a matter of days? And yet the lithsphere, hydrosphere, and atmosphere are intact? Gonna be a hard sell.
My plan was to have the main character abducted to another planet from Earth and told it was destroyed via [plot device here]. The character believes his abductors for a while, until he notices a suspiciously large amount of men and resources shipped to the supposedly void-of-life Earth. He stows away, and finds out that the civilization of his abductors is invading and enslaving the population of Earth. So, it would be alright if the manner Earth is "destroyed" in seems a bit off. In fact, it may even be better that way.
Does it need to be explained? I guess that's a question more of genre than of the story you want to tell, but yeah...you don't necessarily need to spell out what has happened to make it work. Consider Time of the Wolf or The Road - both manage to convey the idea of apocalyptic/post-apocalyptic settings without explicitly naming or describing the apocalyptic event itself. Just assert the fact - all life on Earth has ended in the past day or two - and go from there. That said, good luck getting that to fly with the hard sci-fi readers...
I thought you wanted to destroy life on earth. That means no population for slavery. You need to be clearer. If it's an alien technology that is going to destroy life, you could have anything. You could have them shift the planet 0.1AU away from the sun, which I think would be far enough away for everything to freeze and die. Not sure how long that would take though...
Micro-organisms exist everywhere in and on our planet. They've found them in ice bores, in core drills, in petroleum. There's one called a rotifer that can collapse its internal system and go dormant for decades. In this dormant state, they could be burned in magma, blasted with more radiation than a nuke would produce and then snap-frozen, and they'll still get back up when they've thawed out or moistened up on a temperate food source. Anyway, if it's alien tech, then possibly just blanking the sun out for a couple days to kill off life and freeze the atmosphere. Won't get rid of microlife- nothing will, as long as earth has a molten core- but it'll get rid of almost everything else. Not that the atmosphere will be breathable until it melts again, and it won't have the same stuff in it anymore- it probably won't be breathable.
Ummm, they've only managed to dig 12km into the crust. So there's no proof of micro organisms existing in our planet. The pressures in the cores are much more than the pressures in the deepest oceans so I'd have to second Cogito on this one...
At 5000-7000 degrees celsius, the organic chemicals necessary for carbon based life will not survive. Those are the temperatures at the core of the planet.
as A2 noted, you're contradicting yourself... better get it clear in your head exactly what you want, before asking for advice on how to make it work... as for what could end all life on earth, do you mean animal only, or plant life, as well?... the truth is, anything that could wipe out all animal life, would almost have to do the same to plant life, as well... and to do it in only a couple of days really limits your options... you'd have to dream up some as yet unheard of method, i think, as all scientifically possible ones would take much longer than 48 hours to end all life everywhere...
so you want a plausible reason that doesnt actually happen, but the aliens claim happens, to keep him quiet while they invade? (others have made some of these suggestions) asteroid would do it. super volcano would have to be really massive, but could work. wandering black hole passes through the solar system, close enough to earth to rip it up without actually destroying it (about as unlikely as it gets) nuclear winter (maybe the lack of radiation is his first clue that something's up). plague.. maybe the population aren't dead but there's no cure so they're quarantined? nobody can return (Except the aliens are).
Actually, something's just occurred to me. You could have the aliens set off every one of Earth's nukes, creating a nuclear winter. Then the aliens could take the astronaut away, and due to the near-lightspeed that they travel, 48 hours could pass for the astronaut, but it could be 100 years on Earth. Probably more than enough for everything to be wiped out and it to be almost habitable again. Just a thought.
maybe something nobody's though of yet like a "grey goo" scenario or even that humans have merged themselves with computers until there is no need for physical bodies, then their sentience no longer driven by biological urges has no qualms in simply terminating itself because it has no existential purpose. That would be far out.
You ever hear of Nemesis? It's supposedly a red dwarf star that is in binary synchronize orbit with our sun beyond the Oort Cloud, and passes by the Earth every 50 million years or so. As far as I know of there's not direct evidence to support it, just a theory based on some data about that sun that doesn't add up to what we do know. Well.. that and the projections show that the last time it would have showed up with Earth in range was around the last great extinction during the age of the dinosaurs. EDIT: Resources online at a quick google.. http://en.wikipedia.org/wiki/Nemesis_(star) http://www.space.com/scienceastronomy/solarsystem/nemesis_010320-1.html Nothing currently states that Nemesis exists, but in a story.. eh *Shrugs* you could always say otherwise.
dude, Super-Ebola. Kills people within like a week. Very contagious. Only one or two isolated outbreaks in quickly quarantined parts of Africa, but at least it's real, and kinda fits your scenario. Or does it? Aliens lying to a dude while they enslave mankind? why the hell would they lie to him instead of just enslave his ass to work in the Siberian Ice mines along with the rest of his pathetic species? That premise don't make no sense, but if you wanna kill off all the people on earth, then Super Ebola is the way to go.
you need to see this [i just caught it last night on the history channel]: The Universe : 10 Ways to Destroy the Earth http://www.history.com/content/universe/episode-archive
