Formation and early history

Summary

Mars formed about 4.5 billion years ago along with the other planets. Its early history is commonly divided into major geological periods that reflect changing surface conditions and internal activity. During the Noachian period (roughly 4.5 to 3.5 billion years ago), Mars’s surface was heavily shaped by meteor impacts, valley formation and erosion, possible water oceans, and the loss of its magnetosphere. In the following Hesperian period (beginning about 3.5 billion years ago and ending roughly 3.3–2.9 billion years ago), Mars experienced widespread volcanic activity and flooding. These processes helped carve large outflow channels across the planet. The Amazonian period, which continues to the present, is characterized by the remaining influence of earlier processes and the dominance of ongoing geological activity, with current research still investigating whether Mars ever hosted life or may still show traces of it.

Key Points

• 1

  Mars formed approximately 4.5 billion years ago.

• 2

  Noachian history (4.5–3.5 billion years ago) featured heavy impacts, erosion/valley formation, possible oceans, and loss of the magnetosphere.

• 3

  Hesperian history (starting ~3.5 billion years ago) was dominated by volcanism and flooding that created large outflow channels.

• 4

  Amazonian history continues to the present and reflects the ongoing, remaining influence of earlier geological processes.