What Do We Mean by the Period of Heavy Bombardment

question 161

Multiple Choice

What do we mean by the period of heavy bombardment in the context of the history of our solar system?

• A) The first few hundred million years after the planets formed, which is when most impact craters were formed
• B) The time before planetesimals finished accreting into planets, during which many growing planetesimals must have shattered in collisions
• C) The time during which heavy elements condensed into rock and metal in the solar nebula
• D) The period about 65 million years ago when an impact is thought to have led to the extinction of the dinosaurs

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Definitions:

Autocrine Chemical Messengers

Signaling molecules secreted by cells that bind to receptors on the same cell, leading to a response.

Paracrine Chemical Messengers

Substances released by cells that affect other nearby cells, allowing for local cell communication.

Placental LH-like Hormone

A hormone produced by the placenta that is structurally similar to luteinizing hormone (LH) and supports the corpus luteum, maintaining the production of progesterone during early pregnancy.

Trimester

A term describing a period of three months, often used to divide the nine months of pregnancy into three stages, each with its own developmental milestones.