That's like saying that there is no proof that the sun doesn't orbit the earth in the 17th century.
There is quite a wealth of evidence, which in itself is proof.
There doesn't have to be a body, or a murder weapon, or a witness for enough "proof" to decide in a court of law to put a human being to death for a crime. All it takes is enough evidence to "prove beyond a reasonable doubt". You admit that it is beyond a reasonable doubt, so in a court of law that would equate to proof.
Ok first off, you attempt to use another example that already contains proof of it's existence, the sun and the Earth. The evidence of both is there readily available to all.
Second, if you have evidence, then by all means post it. I see you suggesting there is but don't bother to post a single shred of it. Third, evidence in the court of law is by far no where the same as scientific evidence for proving X. For example, in a court room a witness can testify to seeing something and have that counted as evidence. In science, first hand eye witness testimony is not considered viable evidence.
NDT can put it best in terms of eye witness testimony, start around the 3 min mark
The burden of proof at this point is on those that believe that it could only happen once in a trillion times; that believe it's a miracle that in a DNA strewn soup of molecules where stars and planets form some of the complex organic matter happened to land on a rock the size of a planet between the distance of Venus and Mars relative to it's star's energy output.
Just like there is overwhelming evidence that atoms, electrons, and quarks exist, there is overwhelming evidence that life is common in the galaxy even though it hasn't been directly observed.
Wrong the burden of proof is on those that say there is proof to begin with. Again odds are there is life beyond Earth, I believe this highly but the simple FACT is, we currently do not have proof. As for atoms, electrons and so on, at one point, we had theories of such but we didn't have the proof. Over time proof was gathered, it may have always been there but it wasn't known and wasn't within our reach to gather it. So in a sense if there is proof of alien life, we just don't currently have it. So unless you can provide said evidence, then you're talking out of your ass by saying there is a wealth of it.