They would know if they see anything like traces of water or anything else that would be nessecary for a living organism to have. They look for these with technology like the hubble telescope as well as the drone on Mars to gather as much information as possible.
Hey there are you going home
Answer:
You have external defense systems, which include your skin, tears, mucus, saliva, stomach acid, cilia (small hairs) and helpful bacteria. The skin, nails and hair form the integumentary system, which stops dirt and pathogens from entering the body.
I think The second step of cellular respiration is the Kreb's cycle and it occurs in mitochondrial matrix.
First step of cellular respiration is glycolysis and it occurs in the cytoplasm of a cell.
I am not really confident about my answer.
If I am wrong please correct me. <span />
