Sure, it can (and probably should) be used elsewhere, but the contemporaneous motivation is Iran. The article makes this clear but, this being slashdot, I guess no one bothered to read it.
A laser interferometer in interplanetary space could have an enormous path length quite easily, and would not sense all the vibrations on Earth. It could also be in 3-dimensions, consisting of a satellite hub and 3 corner-cube mirrors at long distances from the hub
Mostly correct. One of the main hurdles, however, is controlling the positions of the spacecraft relative to each other to extremely tight tolerances. In deep space this isn't too difficult. In Earth or Lunar orbit, it's quite difficult. An Earth-Sun lagrange point can work, except that those, too, require some station keeping.
It's not impossible; merely hard.
The dream of having a farm with solar panels, converting water to hydrogen to store in tanks in the ground is a cool dream. You can then use that hydrogen to power your car or heat your home.
It is a cool dream, but handling liquid hydrocarbons is a lot easier. If you have a good way to produce lots of hydrogen, you can 1) use it to synthesize hydrocarbons, which our existing infrastructure can handle, or 2) compress it to technologically challenging pressures or cryogenic temperatures, and still have lower energy density. You don't need pure hydrogen to run a fuel cell - a variety of fuel cells you can buy today for powering a home or datacenter run on natural gas.
in Philae's failure to stick to the surface and it's subsequent journey into the pit of doom
Wait, I thought it was the pit of despair.
[clears throat] Don't even think about trying to escape.
It is "Die Welt", not "Der Welt." For heaven's sake, when you click on the link, the correct name is right there on the top of the page in 48-pt font. How do you screw that up?
In German, "der" and "die" are both articles that translate to the English "the," but they have different genders and should not be conflated. ("der" and "die" have more expanded meanings and uses than just "the", but we'll skip that for now.) It would be similar to an American referring to Donald Trump, Barack Obama, Chuck Norris, or Hulk Hogan as "she".
1. It is a communications relay to Earth. This is probably sufficient justification by itself.
The MAVEN orbiter also serves as a communications relay. As a matter of fact, getting it to Mars to take over communications was deemed so important the launch was allowed to proceed during the last government shutdown.
Of course, when MRO finally kicks the bucket, the U.S. program will be down to just MAVEN for communications. So we should, as you say, have another orbiter ready to take over for continuity's sake.
"Stupidity, like virtue, is its own reward" -- William E. Davidsen