Today cold, dry, we know that Mars was once habitable, but when was that time? Until recently, the scientific community agreed that Mars' magnetic field disappeared about 4.1 billion years ago, leaving the planet vulnerable to cosmic rays and other harmful elements. However, a new study sheds new light on this question. Using computer simulations, researchers suggest that the Martian magnetic field may have persisted until 3.9 billion years ago, extending Mars' habitability window by several hundred million years.
The disappearance of the Martian magnetic field: a crucial turning point
Until recently, the scientific community agreed that Mars' magnetic field disappeared approximately 4.1 billion years. This period represents a crucial turning point in the evolution of the Red Planet, marking the transition from a potentially habitable Mars to the hostile environment we know today.
The magnetic field is in fact essential to the protection of a planet against harmful elements. On Earth, for example, it acts as a shield that deflects charged particles emitted by the solar wind and cosmic rays, radiation that comes from distant stars and powerful cosmic phenomena.
Without an adequate magnetic field, a planet therefore becomes vulnerable to these external threats. On Mars, the absence of magnetic protection would then have led to a significant erosion of its atmosphere and caused a gradual loss of essential elements for life, such as water and organic compounds, as well as a reduction in atmospheric pressure. This phenomenon would ultimately have led to a drastic drop in temperatures and transformed Mars into a barren desert.
New perspectives
A new study by Harvard researchers calls this timeline into question. This work is based on principles of paleomagnetism which studies the prehistoric magnetic field of a planet. The team examined impact craters on the surface of Mars, known to have weak magnetic fields. These craters have been used to infer information about the history of the planet's magnetic field. By analyzing these formations, the researchers hypothesized that these impact basins had formed at a time when the magnetic field was still activemore was going through a polarity reversala phenomenon known on Earth where the north and south poles exchange positions.
In other words, the researchers question the idea that the magnetic field stopped prematurely. Instead, they propose that the impact craters formed in an environment where Mars' dynamo was still operating, albeit in a state of reversed polarity. This could explain why these craters show weak magnetic signals, providing a framework for understanding the evolution of the Martian magnetic field.
Based on their work, the researchers suggest that the Martian magnetic field could have persisted until 3.9 billion yearsthus extending the window of habitability of this planet at least 200 million years old. These results could then influence future space missions, particularly those aimed at exploring traces of ancient life on Mars. Understanding the planet's geological and magnetic history could also guide scientists in the search for exploitable resources for future human missions.
