4. Mass Effect 3 Planet/System Scanning A-HA

This page has pictures of where everything you can find via scanning clusters it. Important items are underlined. "Important" means it is either a war asset or an item that can be turned in for a quest that gives war assets. Fuel/credits/upgrade don't factor into any achievements, so it's up to you whether to get them. All systems aren't available at the start. Some systems/clusters might not be in your game if you don't have DLC. New systems seem to appear after certain missions, or perhaps randomly. The best way to see if you have everything available if to highlight a system and it'll have a % by it, if it's anything but 100% you are missing stuff. If you don't see a system or planet listed here, I found nothing there.

Press to scan. If done near something that can be collected a red circle will appear. Scanning in a system occupied by reapers runs the risk of alerting them, shown by the red bar in the bottom left. If reapers are alerted and they catch you, game over. If you run out of fuel, you are only taken to the nearest mass relay. You can buy fuel or warp to somewhere that sells fuel, so there is no real penalty.

AETHON CLUSTER

Aru

Book of Plenix
Volus Fabrication Units
Fuel

Esori

Volus Dreadnought Kwunu
Fuel

Nura

Volus Intelligence Archives
Fuel

Satu Arrd

Volus Engineering Team
Fuel

Apien Crust System

Castellus

Banner of the First Regiment
Fuel

Gemmae

Turian 79th Flotilla
Fuel
Fuel

Arcturus Stream

Arcturus

Intel from Battle of Arcturus
Fuel

Euler

Fuel

ARGOS RHO

Gorgon

Advanced Power Relays

Hydra

Haptic Optics Array
Fuel

Phoenix

Turian Spec Ops Team
Fossilized Kakliosaur
Fuel

ATHENA NEBULA

Ialessa

Asari Engineers
Fuel

Orisoni

Asari Research Ships
Fuel

Parnitha

Asari Cruiser Cabeon
Fuel

Tomaros

Asari Cruiser Nefrane
Fuel

Vernio

Hesperia Period Statue
Fuel

ATTICAN BETA

Hercules

Interferometric Relay
Fuel

Theseus

Exogeni Scientists
Fuel

CALESTON RIFT

Aysur

Fuel
The other thing is involved with the main DLC story, no spoilers!

Balor

Synthdiamond Heat Sinks
Fuel

CRESCENT NEBULA

Lusarn

Fuel
Credits

Tasale

Liquid Assets
Fuel

EXODUS SYSTEM

Asgard

Alliance Cruiser Shanghai
Alliance Naval Exploration Flotilla
Alliance Spec Ops Team Delta
Remains of a Reaper Destroyer
Fuel

Utopia

Pothean Data Filesp
Fuel

GEMINI SIGMA

Han

Fuel
Credits

Ming

Alliance Crusier Nairobi
Fuel

HADES GAMMA SYSTEM

Antaeus

Fuel
Credits

Cacus

Credits
Fuel

Dis

Fuel
Credits

Farinata

Alliance Frigate Agincourt
Fuel

Plutus

103rd Marine Division

HADES NEXUS

Hekate

Alliance Frigate Hong Kong
Fuel

Hoplos

Obelisk of Karza
Fuel

Pamyat

Alliance Frigate Lepyzig
Fuel

Sheol

Prothean Sphere