Mass Effect 2

This is an entire list of missions that you can find by scanning a planet or locating an item. Do any one of these missions from the list for the achievement to unlock.

Cluster -- System -- Planet -- Mission Name -- Found/Scan

Caleston Rift -- Solveig -- Sinmara -- Endangered Research Station -- Scanned
Caleston Rift -- Talava -- Taitus -- Mining The Canyon -- Scanned
Crescent Nebula -- Lusarn -- Tarith -- Blood Pack Communications Relay -- Complete Patriarch and Deliver Datapad assignments for Aria on Omega
Crescent Nebula -- Zelene -- Helyme -- Captured Mining Facility -- Scanned
Eagle Nebula -- Amun -- Neith -- Wrecked Merchant Freighter -- Scanned
Eagle Nebula -- Strabo -- Jarrahe Station -- Abandoned Research Station -- After Neith
Hourglass Nebula -- Faryar -- Daratar -- Eclipse Smuggling Depot -- Scanned
Hourglass Nebula -- Ploitari -- Zanethu -- Estevanico -- Scanned
Minos Wasteland -- Fortis -- Aequitas -- Abandoned Mine -- Scanned
Omega Nebula -- Arinlarkan -- MSV Strontium Mule -- MSV Strontium Mule -- After Joab
Omega Nebula -- Fathar -- Lorek -- Lost Operative -- Emailed to you
Pylos Nebula -- Dirada -- Canalus -- Anomalous Weather Detected -- Scanned
Rosetta Nebula -- Enoch -- Joab -- Archeological Dig Site -- Scanned
The Shirke Abyssal -- Xe Cha -- Zada Ban -- Blood Pack Base -- After Tarith
Sigurd's Cradle -- Decoris -- Sanctum -- Blue Suns Base -- After MSV Strontium Mule
Sigurd's Cradle -- Skepsis -- Franklin -- Javelin Launch -- Emailed to you
Titan Nebula -- Haskins -- Capek -- Hahne-Kedar Facility -- After Jarrahe Station

Das Kuhnen points out that any DLC missions that pop up (i.e. the Normandy Crash Site and Firewalker Missions) count towards this achievement as well.

This achievement can easily be gained within the first hour to two hours of gameplay or less, depending on how fast you steam through the game. Upon entering Omega and finding out about the Doctor/Archangel, you will gain a mission leading you to an unexplored system called Fathar. Scan the three planets in that system and you should find a disturbance, once you track down where its coming from you'll be able to land your ship on the planet, clear the area of enemies, track down the computer and voila the achievement will be yours once the mission ends.