Complex sentence: Once there, they discovered a very weak Wraith distress signal and Major Sheppard and Dr. McKay convinced Dr. Weir to let them investigate, arguing that despite the signal being likely at least 10,000 years old, any scientific and military knowledge they might find may be useful.
Split into simpler sentences: Once there, they discovered a very weak Wraith distress signal and Major Sheppard and Dr. McKay convinced Dr. Weir to let them investigate. Even if the signal was probably 10,000 years-old, any scientific and military knowledge they might find may be useful.