Water covers 71 per cent of the surface of Earth, and most of it – some 96.5 per cent – is contained within our planet’s oceans. The remaining 3.5 per cent is freshwater and therefore drinkable, but most of that – 68 per cent – is sealed within glaciers and ice. Such statistics are well known and equally well trodden, but they’re intriguing nonetheless. After all, Earth is something of an anomaly, given that it’s the only world in our Solar System with extensive, consistent and stable regions of liquid water at the surface – and no one knows exactly how this came to be.
To understand the mystery of Earth’s water, you need to take into account the Solar System’s snow line – the distance from the Sun beyond which water is present as ice. When the Solar System was formed, this line was between the orbits of Mars and Jupiter. Planets that formed within the line would see water turn to vapour; those beyond could accrete water ice. “It is surprising that Earth has so much water because it formed in the inner Solar System, likely within the snow line,” explains Megan Newcombe, assistant professor of geology at the University of Maryland. “The Earth accreted in a region of the solar nebula that was quite near the Sun, and therefore was likely warm and relatively dry. Water ice accretion to the early Earth was probably limited.”
Yet if the newborn Earth’s proximity to the Sun was likely to have left it dry, how and when did the planet produce its water supply? For many years, scientists have proposed that it came in massive quantities from elsewhere in the Solar System, but proof of the exact source has eluded them.
This story is from the Issue 144 edition of All About Space UK.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 8,500+ magazines and newspapers.
Already a subscriber ? Sign In
This story is from the Issue 144 edition of All About Space UK.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 8,500+ magazines and newspapers.
Already a subscriber? Sign In
"We knew that this would be a historic comet"
Astronomer David Levy was immortalised for his co-discovery of Comet Shoemaker-Levy 9 – its impact with Jupiter 29 years ago held the world in awe
CELESTRON STARSENSE EXPLORER DX 102AZ
Innovative technology provides the simplest and quickest solution yet to finding objects to observe, and this instrument will be very popular with beginners
MOON TOUR - COPERNICUS
Get up close to the ‘Monarch of the Moon’
A HUNGRY BLACK HOLE 'SWITCHES ON' AS ASTRONOMERS WATCH IN SURPRISE
J221951 is one of the most extreme examples yet
MYSTERIES OF THE UNIVERSE - WHY DOES JUPITER CHANGE COLOUR?
For years, scientists have tried to work out why Jupiter’s bands frequently move and change colour. Now they believe they’ve found the answer
MARS HELICOPTER PHONES HOME AFTER A 63-DAY SILENCE
Rugged terrain had kept Ingenuity from communicating with its robotic partner, the Perseverance rover
SIX OF THE BEST SPACE PRANKS
It turns out that the sky isn’t the limit when it comes to a good old-fashioned practical joke
CLIMATES CHANGE IN THE SOLAR SYSTEM
Alongside Earth, our planetary neighbourhood is changing. But not for the better…
TIME APPEARED TO MOVE FIVE TIMES SLOWER IN THE FIRST BILLION YEARS AFTER THE BIG BANG
Time dilation, brought about by the relativistic expansion of space, has resulted in the observed slowing of ‘clocks’ in the early universe
WHAT CAN WE DO WITH A CAPTURED ASTEROID?
Asteroids could provide us with rare resources