Comet 67P Contains Numerous Fossil Cells and Tissues.

Added on Sept. 10: Definitions of  low/high molecular weights and macromolecules.
Low molecular weight: lighter than 900 daltons. Molecules lighter than 900 daltons are called small molecules . In astronomy, complex organic molecules refers to molecules with multiple carbons, such as amino acids, which are no heavier than 205 daltons. Simple organic molecules are those lighter than 100 daltons.
High molecular weight: heavier than 900 daltons. Molecules heavier than 900 daltons are called large molecules. Macromolecules surely possess high molecular weights as explained below:
Macromolecules: (https://en.wikipedia.org/wiki/Macromolecule)
“A macromolecule is a very large molecule, such as protein, commonly created by polymerization of smaller subunits (monomers). They are typically composed of thousands of atoms or more. The most common macromolecules in biochemistry are biopolymers (nucleic acids, proteins, carbohydrates and polyphenols) and large non-polymeric molecules (such as lipids and macrocycles).”