The Wreckage is a decorative object that appears in the first mission attached in a big asteroid,

Wreckage seen in an asteroid
and in seventh mission after the Transporter Ship explodes. It appears to be a wrecked Shuttlecraft .

Debris spreading after destroying wreckage, before they explode.
When destroyed by player, it splits into Debris, who explode in less than a second.
Debris also appear in mission 3 if a shuttlecraft gets destroyed.
Wreckage seen in mission 7 after Transporter Ship explodes