The habitat of a planet depends on many factors. One is the presence of a strong and long life magnetic field. These fields form thousands of kilometers below the planet’s surface in its liquid form and extend into space – protecting the atmosphere from harmful solar radiation.
Without a strong magnetic field, a planet struggles to hang in a breathless atmosphere – which is bad news for the life we know. A new study, published in Science Advances, suggests that the now lost Moon is a magnetic field that could help protect our planet’s atmosphere as life formed about 4 billion years ago.
Today, Earth has a powerful global magnetic field that protects the atmosphere and low-orbiting satellites from harsh solar radiation. In contrast, the Moon does not contain either a breathing atmosphere or a global magnetic field.
Global fields are formed by the movement of molten iron at the cores of planets and moons. Maintaining fluid movement requires energy, such as heat trapped inside the core. When there is not enough energy, the farm dies.
Without a global magnetic field, the particles of solar wind (radiation from the Sun) passing near a planet form electric fields that can accelerate the charged atoms, known as ions , outside the environment. This process is now happening on Mars and it is losing oxygen as a result ̵1; something that is directly measured by the Mars atmosphere and mission change (Maven) mission. Solar wind can also strike the air and knock molecules into space.
The Maven team estimated that the amount of oxygen lost from the Martian atmosphere throughout its history was equivalent to content in a global water layer, 23 meters thick.
[Read: The Moon’s surface is rusting — and Earth may be to blame]
Application of ancient magnetic fields
New research investigates how early Earth and Moon can interact. But investigating these ancient fields is not easy. Scientists rely on ancient rocks that contain particles that are magnetized as rocks form, which saves the direction and strength of the magnetic field at that time and place. Such stones are rare and the acquisition of their magnetic signal requires careful and delicate laboratory measurement.
However, such studies have shown that the Earth has developed a magnetic field even in the last 3.5 billion years, and possibly up to 4.2 billion years, with a mean strength of more than half the current value. We do not know about how the field behaved earlier than that.
In contrast, the Moon’s field was probably much stronger than Earth’s around 4 billion years ago, before finally descending into a weak farm state to 3.2 billion years ago. Currently, little is known about the structure or time variation of these ancient fields.
Another complexity is the interaction between the lunar and geomagnetic fields. The new paper, which models the interaction of two magnetic fields with poles to the north either aligned or vice versa, shows that the interaction extends to the region of the neighboring Earth space between our planets and Sun protected from solar wind.
The new study is an interesting first step towards understanding how important these effects are when averaging a month orbit or hundreds of millions of years that are important for the analysis of planetary habitat . But to be sure we need more modeling and more measurements of the strengths of the early magnetic fields of the Earth and Moon.
What’s more, a strong magnetic field does not guarantee the continued availability of a planet’s atmosphere – surface and deep inner environments are important, as well as influences from space. For example, the radiance and activity of the Sun has evolved over billions of years as well as the ability of the solar wind to dissipate atmospheres.
How each of these factors contributes to the evolution of planetary habitat, and therefore life, is still not fully understood. Their nature and how they interact with each other is likely to change over geological times. But fortunately, the latest study has added another piece to a fascinating puzzle.
This article is republished from The Conversation by Christopher Davies, Associate Professor of Theoretical Geophysics, University of Leeds and Jon Mound, Associate Professor of Geophysics, University of Leeds under a Creative Commons license. Read the original article.
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