What happens if during the 2000s microbial life is found on a moon in the Solar System?
How? Are you postulating a massive increase in Planetary Science budgets? Because that's what it would (have) take(n).
The only lander that landed on a moon in the 2000s was Huygens, so that narrows the list of sites of discovery to Titan. I suppose Huygens drops into one of the methane lakes and discovers some sort of methane-based microbes. Not sure if any of the instruments could do that, but let's say they could.
Looking at the set of instruments on Huygens, I don't think there's any way life COULD have been detected. And since Titan wasn't one of the moons generally considered to be possibly life bearing, even if they had expanded the probe to take other instruments, a 'life detector' (what ever that might be) wouldn't likely be one of them.
Were they not found already?
I seem to recall reading an article about how they already found some microbes. Or was it just some hoax?
No. People found what they THOUGHT were microbes in meteorites believed to have come from Mars, but it's generally understood now (iirc) that these are abiological in origin. (They were way too small for bacteria, for one thing.)
It depends on where the microbial life was found. No doubt NASA, ESA and other space agencies with the capability would begin focusing the unmanned program on the body that the life was found on.
If the life is found on Venus (it's possible that microbial life exists in the clouds of Venus, at certains altitudes the air-pressure and temperature levels allow liquid water, it's also possible for some evidence of past life to be found on the surface) then it's certain there would be plans for atmospheric balloons, orbiters, landers maybe even rovers being sent to Venus. Talk would immediately begin about human missions to Venus orbit with real-time tele-operated probes in the atmosphere/surface.
If life is found on Mars (either past fossilized life or extant life underground or dormant life on the surface) there will be even more focus put on exploring Mars and the case for human missions will be increased dramatically (with some kind of Mars-Semi Direct mission happening a decade later). Sample Return would be a big priority before the Manned Mission.
If life is found on Europa, Callisto, Ganymede or anywhere else in the Jupiter system, you can bet the next flagship would likely be a lander with some kind of melt-probe. Alternatively, a sample return mission might be launched. Advanced concept studies of a manned mission to the Jupiter system would be made but not actually funded in the near-term.
If life is found on Titan, I imagine the idea of a lake-lander or atmospheric balloon might be popular. A dedicated Titan orbiter would be another possibility.
If life is found beyond Saturn the options for unmanned missions become limited. The Discovery of Life would likely be so important that an extremely advanced JIMO like nuclear-ion propelled flagship mission would likely be sent despite the cost, mission complexity and technological difficulty.
If we're talking about the discover of life on an exo-planet, advanced space telescopes would be sent up. Eventually a telescope could be sent to the Solar Gravitational Focus point. An interstellar probe capable of reaching another exoplanet is a sufficiently distant prospect that it would remain atleast decades in the future if not a century or more. An Interstellar Precourser Probe to reach 200 AU might be sent before the 550 AU gravitational lense telescope mission. Most of the investment would be in advanced space telescopes.
Yabut. To FIND life, you have to LOOK for it. The ONLY place in the solar system we've even looked is Mars. Yes, there could be life on Mars. Yes, we might have found it if 1) it exists and 2) we were very lucky.
But given the incredible expense of planetary probes, the massive competition for instruments to go on them, and the incredible mass constraints, I can't see most probes getting a 'life detector' instrument unless we have good a priori reasons for believing life might exist there.
Moreover, almost all cases require said probe to be on a lander. Given the number of even Orbiters we've sent out (small), increasing the number (and mass) of landers to enable such a discovery almost certainly would require that massively greater (2x or more) money had been plowed into Planetary Science.
Now. If you want to discuss what might happen when we do get such instruments there, that's one thing - but then the thread belongs in Future History, not here.