In the near future a group of explorers land on Mars and proceed to explore the cave system under Pavonis Mons.
While exploring the gigantic interior of the lava tube, sensors indicate the presence of an unexpected kind of emission. Using remote probes they detect radiation levels that are safe for humans - but still, being on the safe side, they continue to explore using drones only.
They manage to locate the source while exploring the deepest parts of the cave system. As they send in a tethered drone packed full of sensors (CCDs, spectrometers, radiation detectors, environmental detectors and atmospheric detectors, among others) a huge stream of data start to pour from the sensors into the expedition computers as the science officer orders it to focus on a central piece standing atop what looks like a obsidian pillar; It clearly look like an artificial object.
The drone maintain its emotionless glare as the science officer asks for a few more minutes to analyze the incoming data, followed by a request for a couple more hours - and finally another for a day.
The science team then communicates to mission command, to the shock of all involved personnel, that the data points to an extra-galactic origin.
Question: How could they, based on remote sensory information only, reach this conclusion?
- Near-future technological resources (2051-2100)
- The device may be resting, slotted in or kept stable/in place by a powered mechanism
- The drone packs a modern, beefed-up, expanded version of the MSL Science Payload in a sleek yet super creepy crawling body.
(Given the interesting points of view of some answers I dropped the
hard-science tag, but would still like to keep it reasonably not so mushy.)