1-2 MARS
1-2 Mars is the 2nd stage of Cosmos Ch.1 — Beyond the Exosphere. Previous stage: 1-1 Earth. Next stage: 1-3 Jupiter.
Hyppoh, Shibalien, Shibalien Elite and Helmut Krabbe are Alien. Anti-Alien units take less damage and deal more.
GROSS CAT A Its True Form is Strong Against Alien, giving budget anti-Alien value. 
LI'L GROSS CAT B True Form has a 30% Knockback vs Alien. 
WHEEL CAT A Deals Massive Damage to Alien enemies — a huge area nuke against Alien crowds and bosses. Also fits “Clear the crowd.” 
SURFER CAT A Area Freeze vs Alien controls Alien groups. Also fits “Clear the crowd.” 
CATMAN S Deals Massive Damage to Alien in every form. Also fits “Clear the crowd.” 6 enemy types stack up here. Area attackers hit the whole push at once instead of one unit at a time.
VALKYRIE CAT A Hits the whole group while it freezes them. WHEEL CAT A Hits every Alien in a wide area at once, melting grouped Star Aliens. Also fits “Counter Alien.” SURFER CAT A Area damage hits grouped enemies. Also fits “Counter Alien.” CATMAN S Long-range Area damage clears groups. Also fits “Counter Alien.” 
ACTRESS CAT B Hits multiple enemies at once for budget crowd damage. First rarity-restriction stage — Specials banned. Wiki-verified enemy mix: Snache, Those Guys, Shibalien, Helmut Krabbe, Shibalien Elite, Hyppoh. Easy with most ItF Anti-Alien Treasures collected.
First gate stage in CotC: No Specials. r/battlecats's universal advice for this one is 'this is where you find out if you've been one-tricking with Bahamut Cat.' Bahamut Cat, Awakened Bahamut, Crazed Bahamut — all Specials, all banned. (Mohawk Cat is Normal and Manic Mohawk is Super Rare; both stay legal.) Suddenly you're playing with Normal/Rare/SR meatshields and your Uber/LR roster. Standard loadout: Normal Cat + Tank Cat + Wall Cat + Crazed Wall (Super Rare, legal here) as meatshields → Anti-Alien Ubers as the entire damage stack (Bazibastra, Lumina, Mighty Reza, talented Anti-Alien Rares like Boogie Cat). Common failure: realizing mid-stage that your favorite meatshield is Special and you can't deploy it. Build your no-Specials lineup before queueing.
The castle you destroy to clear the stage.