In 1965, Contraves Italiana began work on an improved missile, Vulcano, which used the same guidance system, but included a two-stage (booster + sustainer) rocket motor to give a longer (25 kilometres (16 mi)) range.

[7][8] Testing of Nettuno began in 1966,[9] with a trial installation being made on the Freccia-class patrol boat Saetta of the Italian navy, with the five-round launcher replacing a Bofors 40 mm gun.

[13] No other sales of the ship-based version were made,[1] but development of Sea Killer Mark 2 into an all-weather anti-ship missile to equip the Italian Navy's helicopters began in 1967,[14] with the helicopter-based weapon system being named Marte.

[16] The Marte ER, an improvement on the missile family, replaced the rocket motor with Williams WJ-24-8G turbojet propulsion and added a new ISO-caliber cylinder cell, which made it shorter in length but extended its range to over 100 km (62 mi; 54 nmi).

In November 2015, a Eurofighter Typhoon was fit-tested for a fixed-wing version of the missile called the Marte-ERP, which does not feature folding fins and sheds the booster for a larger 120 kg (265 lb) warhead with penetrating and sector-blast properties; though smaller than other options like the Harpoon and RBS-15, a fighter like Eurofighter Typhoon can carry six Marte-ERPs (or four with fuel tanks) compared to two or three larger missiles.