fastq file format unknown
This indeed looks like some sort of binary file. I have seen bunch of those when people renamed .fastq.gz to .fastq without actually uncompressing them. However, as you say, this is not your case, as file pair1.fastq would identify the file as gzip compressed data.
Looking at possible return values of file comments here, data basically mean the command could not figure out anything about it beside being some sort of binary data file, but I suspect it probably somehow broken file. Honestly, at this point I think you should check the source of the data. If it's from a public database, re-download the data. If it's your own sequencing, contact the sequencing provider and check the data with them. I don't see any way to rescue this file (which does not necerasrily mean there is nothing you can do).