Debris Field

From OGame Wiki

A debris field is created after a battle takes place, and contains 30% of the resources worth of all the ships that were destroyed in the battle (this does not include transported resources). If the debris field contains more than 100k resources, there is a chance that a moon will be formed. This chance increases by 1% for each 100,000 more resources in the debris, to a maximum of 20%.

Only metal and crystal go into debris fields.

You can reclaim this debris by building recyclers and sending them on a harvesting mission. Each recycler can take 20,000 units of resources and you simply hover over the debris field and a table will appear showing you how many resources are in orbit. You simply divide the total by 20,000 and round up to the nearest number to get the amount of recyclers needed, then you send them in the Fleet Screen. Recylers can only be sent to debris fields, if there is not one at the coordinates then there will be an error and your fleet will not be sent. It is possible to send ships to a debris field that does not show up in the galaxy, any field with less than 300 total resources does not show up however can still have a mission sent to it even if it has 0. All debris fields less than 300 are reset on monday at 1 AM server time.

OGame Commander users can just click on the debris field and it will send the appropriate amount of recyclers to the debris field automatically, assuming you have them stationed on the planet.