A Timeline For Planet Formation (Page 2 of 2) in pdf

A Timeline For Planet Formation Page 2

Answer Key

Problem 1 – If the Pre-Solar Nebula Era occurred 4.6 billion years ago, how long ago did the

Rocky Planet Era end?

Answer: On the Timeline ‘0.0’ represents a time 4.6 billion years ago, so the Rocky Planet Era

ended 100 million years after this or 4.5 billion years ago.

Problem 2 – How many years from the current time did the Late Heavy Bombardment Era end

in the inner solar system?

Answer: LHB ended 600 million years after Time ‘0.0’ or 4.6 billion – 600 million = 4.0 billion

years ago.

Problem 3 – About how many years ago do the oldest fossils date from on Earth?

Answer: 4.6 billion – 800 million = 3.8 billion years ago.

Problem 4 – How many years were there between the Planetessimal Era and the end of the

Rocky Planet Era?

Answer: On the timeline the difference is 100 million – 51 million = 49 million years.

Problem 5 – If 80 objects the size of the Moon collided to form Earth during the time period in

Problem 4, about how many years elapsed between these impact events?

Answer: The time interval is 49 million years so the average time between impacts would

have been 49 million years/80 impacts = 612,000 years.

Space Math

A Timeline For Planet Formation Page 2