Wednesday, 21 October 2015

Water in Mars

Liquid water may still flow on Mars, but that doesn't mean it's easy to spot. The search for water on the Red Planet has taken more than 15 years to turn up definitive signs that liquid flows on the surface today. In the past, however, rivers and oceans may have covered the land. 
Observations of the Red Planet indicate that rivers and oceans may have been prominent features in its early history. 
 Mars may have had a denser atmosphere and higher surface temperatures, allowing vast amounts of liquid water on the surface, possibly including a large ocean that may have covered one-third of the planet. Water has also apparently flowed across the surface for short periods at various intervals more recently in Mars' history.

Where is the water today?
Liquid water appears to flow from some steep, relatively warm slopes on the Martian surface. First identified in 2011, features known as recurring slope lineae (RSL) were confirmed to be signs of salty water running on the surface of the planet today. The dark streaks appear seasonally on Martian slopes were found in images taken by the High Resolution Imaging Science Experiment (HiRISE) camera aboard the Mars Reconnaissance Orbiter (MRO) Spectral analysis of RSL lead scientists to conclude they are caused by salty liquid water.
There are also giant river courses considered to have resulted from brief, catastrophic floods, perhaps when a meteorite impact melted large amounts of permafrost, or underground ice, or sent a shock wave through an aquifer.  These are called outflow channels, and are up to tens of kilometres wide.  They start wide and branch downstream, and where they flow over level plains spread out to be hundreds of kilometres across.So there is abundant evidence for the former presence of liquid water, and water ice has been directly observed at the north pole. But estimates of the quantity of water on Mars vary widely.  The leading expert on this subject is Michael Carr of the US Geological Survey. He quotes estimates that range from enough water to cover the whole of Mars to depths of more than 10 kilometres, all the way down to less than 10 metres

Hydrosphere in Mars?

The hydrosphere in Mars is frozen and there is water vapor in the atmosphere Billions of years ago, Mars was a warm and wet world that could have supported microbial life in some regions. But the planet is smaller than Earth, with less gravity and a thinner atmosphere. Over time, as liquid water evaporated, more and more of it escaped into space, allowing less to fall back to the surface of the planet. To discover the possibilities for past or present life on Mars, NASA's Mars Exploration Program is currently following an exploration strategy known as "Seek Signs of Life." This science theme is built on the prior science theme of "Follow the Water,"

How Mars lost its oceans?

About 4 billion years ago, a primitive ocean on Mars held more water than Earth’s Arctic Ocean but Mars has lost 87% of it to space.
A primitive ocean on Mars held more water than Earth’s Arctic Ocean. Most of the water  escaped into space.
An ancient ocean there would have covered 19 percent of the planet’s surface. 
 The researchers distinguished the chemical signatures of two slightly different forms of water in Mars’ atmosphere. One is the familiar H2O. The other is HDO, a naturally occurring variation in which one hydrogen is replaced by a heavier form, called deuterium.
By comparing the ratio of HDO to H2O in water on Mars today and comparing it with the ratio in water trapped in a Mars meteorite dating from about 4.5 billion years ago, scientists can measure the subsequent atmospheric changes and determine how much water has escaped into space.
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