It's difficult to pick just three, as so many incredible spacecraft have explored Mars! Here's a breakdown of some notable missions, with an emphasis on the current exploration efforts:

Current Missions (active as of October 26, 2023):

* Perseverance rover: This rover is currently exploring the Jezero Crater, searching for signs of past life and collecting samples for future return to Earth.

* Curiosity rover: Exploring Gale Crater since 2012, Curiosity has made major discoveries about Martian geology and the possibility of past habitable environments.

* Mars Reconnaissance Orbiter (MRO): MRO has been orbiting Mars since 2006, mapping the surface, studying the atmosphere, and searching for evidence of past water.

Other Notable Missions (past):

* InSight lander: This mission studied Mars's interior from 2018 to 2022, providing unprecedented data on the planet's core, mantle, and crust.

* Opportunity rover: This rover operated for over 14 years, exploring Meridiani Planum and providing valuable insights into Martian geology and the history of water on Mars.

* Spirit rover: This rover explored the Gusev Crater from 2004 to 2010, contributing to our understanding of Martian geology and the possibility of past liquid water.

Ultimately, choosing just three is a matter of perspective. If we focus on current missions, Perseverance, Curiosity, and MRO are the best representatives of the ongoing exploration of Mars.