Oldest Place on Earth: Pilbara Region of Western Australia Is Home to Fossilized Evidence of Earliest Lifeforms

The Earth is believed to be around 4.54 billion years old. It might be considered an old planet, yet the rocky surfaces that make up its land masses can vary greatly in age. Some of these land masses existed several billion years ago, while others were formed within the past 100 million years from molten magma that solidified.

(Photo: Wikimedia Commons/ James St. John)

Due to these differences in the age of land masses, one might wonder where the oldest place on Earth can be found.

How Old is Pilbara?

Pilbara is a large, dry, thinly populated area in the north of Western Australia. It is known for its Aboriginal peoples, ancient landscapes, and vast mineral deposits. This region is also a global biodiversity hotspot for subterranean fauna.

With a geographic area of around 194 169 square miles (502 896 square kilometers), the Pilbara is primarily composed of an arid and rocky landscape. It dates back billions of years, with some of the rock formations dating back more than 3.5 billion years.

Experts have determined that the vast formations of iron-rich rocks in the Pilbara emerged prior to the existence of oxygen and life itself. It is even considered the best-preserved example of the world's most ancient crust. Although other iron deposits in the world are thought to have formed on a similar timeline, the surface of the Pilbara remains undisturbed and unburied by geologically cataclysmic events.

According to geology professor Martin Van Kranendonk from the University of New South Wales, the rocks in the Pilbara are so ancient that they do not contain any fossils within their structures. This is because these rocks started to form in a period when there were no lifeforms, so there was nothing to fossilize. However, the region is home to stromatolites, the fossilized evidence of the oldest lifeforms on Earth.

One of the most iconic geological sites in the Pilbara is the Hamersley Range, a region with deep gorges and iron-rich rocks. Since these rocks have captured the formation process, looking at them is like looking at time. Each of the layers tells the story of the Earth's changing environment.

Clues to Searching Martian Life

As NASA explores the possibility of ancient life on Mars, it looks for clues from some of the oldest lifeforms on Earth. Since Earth's active geological processes routinely recycle its surface, the stromatolites in Pilbara are among the few remaining rocks with preserved remnants of early terrestrial life.

In 2019, NASA scientists explored the Pilbara more thoroughly to prepare for their journey to the red planet. Many of the team members had never personally seen evidence of ancient life, yet that is what they were going to Mars to look for. Seeing and understanding the details and texture of the fossilized stromatolites gave them a better understanding of the signatures of life.

Aside from its age, the chemical similarities of the rock composition meant that the Pilbara was highly relevant to the astronauts' preparation for the Mars mission. When the stromatolites were still alive, they likely developed in a lake environment. The red planet has evidence of past rivers, lakes, and oceans, although it is unclear if there was much free oxygen in its atmosphere. In other words, the clues to the geological past preserved in Pilbara are similar to those that scientists want to explore on Mars as they search for evidence of life.