DEEP UNKNOWN

The Earth's core works as an engine to generate heat for natural processes and produce the planet's magnetism. But as this iron-rich layer gradually solidifies into a ball, what will happen to the planet's habitability? As the world drills into and analyses the Earth's interiors, certain clues about its evolution and state emerge.

- ROHINI KRISHNAMURTHY

THE SECRET that drives the Earth's habitability lies some 2,000-6,000 kilometres below our feet in the core of the planet. We know that the innermost layer of the Earth is slowly turning solid, and as it does, it radiates heat that generates a magnetic field which rises to surround and protect the planet. But all our understandings on the core are based on just hypothesis; there is so much about the Earth's heart that eludes us.

In fact, the world has seen more success in space than in understanding its own planet. US space agency NASA's Voyager 1 spacecraft, launched in 1977, has travelled 23 billion km from the Earth. In contrast, the deepest hole drilled into the planet's surface is just 12.2 km (more on this later). What makes it difficult to conduct physical studies of the core is the unforgiving interiors of the Earth. Human bones could turn into dust at depths of 200 km. The base of the crust has a temperature of around 1,000°C, the bottom of the mantle is 3,000°C and the core is about 6,000°C. The pressure, too, could kill. Studies show it can range from 24-136 gigapascals (1 gigapascal or GPa is 1 billion pascals) in the lower mantle to 135-330 GPa in the outer core and 330-365 GPa in the inner core. Humans can only withstand up to a few thousand KPa (1 kilopascal or KPa is 0.012 GPa).

Therefore, any study that tries to throw some light on the functioning of the core is subject to abject scrutiny. Two such studies, published early this year, have triggered debate and discourse among scientists, while highlighting that we do not yet have the technological resources to reach the deep Earth and gain more concrete insights.