@Eliar I gave you a funny mainly for your use of the word "obviously!"
But seriously, while I bow to no one in my science fiction fandom (though I may be much outdated, still stuck in Golden Age to 1980s stuff for the most part, only CJ Cherryh is someone I still read new stuff from consistently) what are the odds that the spectral chemistry of a practical spaceship of any kind--be it designed as a starship or just some run of the mill workhorse interplanetary hauler as in say The Expanse that happened to accelerate and then failed to decelerate--would match that of asteroids and not be weirdly exotic in some way that stands drastically out? I could ask, what would the spectrum of Skylab or the ISS look like, compared to natural space objects. But of course our space habitats are in the most primitive generations of spacecraft design (or, we hope so anyway!) and who knows what exotic materials we'll be making outer hulls out of several hundred years hence?
All I am saying is, assuming the spacecraft are designed solely for utility, it seems most unlikely to me some combination of advanced hull material with external array junk like solar panels, radiators, sensor arrays etc all merged together into one pixel's worth of spectral data would just happen to come close to the range of spectra we normally observe in asteroids.
To be sure, if the builders had some reason to be deliberately stealthy, disguising a working spaceship as an asteroid would mean it looks exactly that way.
And we can imagine weirder reasons, such as a simple aesthetic choice--ie maybe someone out there thought an asteroid style paint job was cool? God knows what alien lines of reasoning we can't well imagine, not with any confidence anyone would actually think that way anyway, might conceivably apply. (I tend to assume critters evolved in the same material universe as us would find some mental and philosophical common ground with us smooth apes sooner or later, at some level of abstraction and sophistication or other. But I can hardly prove that, can I)?
So I thought saying obviously was obviously a funny dry joke. I assume the object was and is natural. And frankly if some aliens did fly by and not say Hi, I'd be pretty unhappy with them...though again, God knows they'd have plenty of prudent reasons not to tip us off unambiguously like that.
Y'all know about the Voyager probes, and the analog audio record made of gold included on them that Carl Sagan and his wife or partner (I think they were formally married but I hardly care if they weren't of course) wrote about in the book
Murmurs of Earth? Well a couple of related anecdotes about the audio recorded verbal greetings in lots of different languages:
1) per the translations of the recorded greetings given in Murmurs of Earth, I infer the polite thing to say to a person in the Chinese family of languages, many different ones of which were included in the greetings, is apparently to ask them if they have eaten lately. I suppose the implication is if not, the greeter will feed the greeted. Now that is quite a nice approach to politeness! But still...I had to find the notion of us sending a bunch of aliens a record that repeatedly asks them if they have eaten yet, along with a valiant attempt to convey the basic nature of our biochemistry and what our life forms look like as they have now evolved all kind of daring in view of the long SF tradition of aliens coming to Earth to suck our blood (as HG Wells imagined) or simply munch on us wholesale, pretty hilarious in its faith in the basic goodness of aliens! (I'd like to bet that way, and anyway it seems likely to me the biochemistry of life forms evolved on alien worlds, even worlds with gross physical and atmospheric/hydrospheric chemistry parameters very similar to Earth, would be made of poison to us, and vice versa, due to millions of essentially arbitrary chemical "choices" evolution made out of orders of magnitude more options that work more or less equally well. So I don't really think the first species to observe the probe and read its records will actually show up in a horde of starships whose complements all have bibs on and copies of some sort of document whose title translates "To Serve Man!" But you never know, do you?
2) at the other end of the spectrum...A Native American Studies teacher I once knew claimed (accurately I think) that of all the language families included, none are North American Native people. (There is a greeting in Quechua, the language of the "Inca" empire and of Peruvian highland native peoples to this day, but we Anglo-Americans regard South America as a different continent, though I gather many in Latin America regard the Western Hemisphere as having one big nearly but not quite broken supercontinent). He went on to say that Sagan or whoever was collecting the audio clips did approach a Navajo "singer," a kind of shaman, to record something for the aliens. He solemnly complied--as people may know, Dine, the language group shared by the Navajo and Apache, is a very hard language for non-native speakers to learn. But anyway, someone did happen to check the recording and it said something along the lines of "Don't listen to anything these people tell you; they want to come and steal all your land!" So that was left out!
Yep, I want our relations with our Brothers and Sisters in the Sky to be good and mutually helpful ones. But should either we or they actually bet our lives they will be?
