While studying a Martian meteorite, researchers found evidence of the oldest known water on Mars, which dates back to 4.45 billion years ago. The discovery suggests that Mars' geological history includes extensive hydrothermal activity that may have supported habitability early in its history. Trace element analysis of these ancient zircons hinted at conditions that may have formed deposits similar to those on Earth, raising fascinating possibilities for Mars' past.
Water is everywhere on Earth - covering 70% of its surface, permeating the air and even locked in rocks. Geological evidence shows that water has existed stably on Earth for about 4.3 billion years.
However, things are different on Mars. The timeline for water on the Red Planet remains uncertain. Scientists are working to determine when water first appeared on Mars, where it was concentrated, and how long it lasted. If Mars was ever habitable, it would need at least some water.
In a groundbreaking study, we analyzed the mineral zircon in Martian meteorites and found evidence of water dating back to 4.45 billion years ago. The findings, recently published in Science Advances, may be the oldest evidence yet of water on Mars.
Water has long been thought to have played an important role in early Martian history. To put our findings into a broader context, let's first consider what "early Mars" means in terms of Martian geological timescales, and then consider different approaches to finding water on Mars.
Like Earth, Mars formed about 4.5 billion years ago. The history of Mars spans four geological periods. They are the Amazonian (dating back 3 billion years ago from today), the Hesperian (3 billion years ago to 3.7 billion years ago), the Noachian (3.7 billion years ago to 4.1 billion years ago), and the Pre-Noachian (4.1 billion years ago to about 4.5 billion years ago).
In the 1970s, NASA's Mariner 9 spacecraft captured images of river valleys on the surface of Mars, reporting the first evidence of water on Mars. Later orbiting missions, including Mars Global Surveyor and Mars Express, detected the widespread presence of hydrated clay minerals on the Martian surface, which require the presence of water to exist.
Martian river valleys and clay minerals occur primarily in the Noachian terrain, which covers about 45% of Mars. Additionally, the orbiter discovered large flood channels - called outflow channels - in the Hesperian terrain. This suggests the presence of ephemeral water on the Martian surface, possibly as a result of groundwater release.
Most reports of water on Mars are in materials or terrain that are 3 billion years old. There isn't much evidence for stable liquid water on Mars any closer than this.
What about the pre-Neoproterozoic era? When did water first appear on Mars?
There are three ways to find water on Mars. The first is to use orbiting spacecraft to observe the surface of Mars. The second approach is to use ground-based observations, such as those conducted by Mars rovers. A third approach is to study Martian meteorites that have landed on Earth, and that's what we did.
In fact, the only pre-Nuachian material we can directly study exists in meteorites from Mars. Of all the meteorites that land on Earth, a small percentage come from our neighboring planet.
A smaller subset of these meteorites, believed to have been ejected from Mars during an asteroid impact, contains pre-Noachian material.
The "poster child" of this group of meteorites is an extraordinary rock called NWA7034, or "Black Beauty." "Black Beauty" is a famous Martian meteorite composed of fragmented surface material (or debris). In addition to rock fragments, it contains zircons that were formed between 4.48 billion and 4.43 billion years ago. These are the oldest known fragments of Mars.
While studying trace elements in one of the ancient zircons, we found evidence of hydrothermal processes - meaning they were exposed to hot water when they formed in the distant past.
The zircon we studied is 4.45 billion years old. Inside it, iron, aluminum and sodium are preserved in an abundance pattern of concentric layers, similar to that of an onion.
This pattern, known as oscillatory zoning, suggests that these elements were incorporated during the zircon's igneous history, that is, in the magma.
The problem is, iron, aluminum, and sodium are not typically found in crystalline igneous rock zircon, so how did these elements show up in Martian zircon?
The answer is hydrothermal fluids. Zircons with growth zoning patterns for elements such as iron, aluminum and sodium are extremely rare among Earth's rocks. Olympic Dam in South Australia, a massive deposit of copper, uranium and gold, is one of the only places where this phenomenon has been described.
The metals in places like Olympic Dam were concentrated by hydrothermal systems that moved through the rock during magmatic activity.
Hydrothermal systems form wherever hot water heated by volcanic pipe systems flows through rock. The spectacular geysers in places like Yellowstone National Park in the United States are formed by hydrothermal eruptions on the surface of the earth.
The discovery of hydrothermal Martian zircons raises the intriguing possibility of the formation of early mineral deposits on Mars.
Previous research proposed a wet pre-New Age Mars. Unusual oxygen isotope ratios in a 4.43 billion-year-old Martian zircon have been interpreted as evidence of an early hydrosphere. Some even believe that Mars may have had an early global ocean 4.45 billion years ago.
It can be seen from our study that the magmatic hydrothermal system was very active in the early stages of the formation of the Martian crust 4.45 billion years ago.
It's unclear if this means surface waters have stabilized at this point, but we think it's possible. What is clear is that the Martian crust, like Earth's, contained water soon after its formation - a necessary condition for habitability.
Author: Aaron J. Cavosie, Senior Lecturer, School of Earth and Planetary Sciences, Curtin University.
Adapted from an article originally published in The Conversation.
Compiled from /ScitechDaily