In the google keyword tool, down the left side you'll see 'match types'; deselect the 'broad' and select only the 'exact' box. The broad search number means nothing and is hugely inflated. The exact searches are the only relevant numbers.
'facts on space' receives only 320 exact monthly searches.
'facts about space' receives 4400 searches, but is regged in .com and .net.
IMO your domain is worth zero if basing the value on search numbers, traffic, monetizing, etc. To someone who wants to build a website about space facts, maybe reg fee to mid xx. Any higher price, and they'd simply reg a brandable name or get the dot.net. It's not a phrase that has any strong clear use other than a site with vague/general knowledge about space.
If you bought or regged it only for the resale value, I'd let it drop around renewal time. If you bought it because you have an interest in space and in developing a website around it, then the domain has a personal and end user value to you.
Good luck
