How many {material used} are for {atmosphere of Mars} ?
What material can be found in Mars' atmosphere?
What type of material can be used in the atmosphere of Mars?
SELECT ( COUNT ( ?w ) AS ?x ) { resource:atmosphere_of_Mars property:made_from_material ?w }
SELECT (COUNT(?obj) AS ?objs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q218860> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P186> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
} 

SELECT (COUNT(?obj) AS ?value ) { wd:Q218860 wdt:P186 ?obj }
4