The question of whether life ever existed on Mars has inspired scientists – and songwriters – for decades. The Red Planet is currently an arid, icy desert where no sign of life remains, but was it always this way?

It is widely recognised that living entities have three basic requirements: standing water, an energy source and the five chemical elements, carbon, oxygen, hydrogen, phosphorus and nitrogen. Then a very long time for the chemical soup to stew. The rover Curiosity has found evidence of all three in certain areas of Mars, namely the Gale Crater, but were these available for long enough for life to develop?

A few weeks ago, Unknown Country reported that NASA were investing millions of dollars into a new laser-based instrument, located on the International Space Station,  which is intended to provide a unique 3-D view of Earth’s forests. The focus of its mission is to provide definitive information about the role of forests in the carbon cycle, and as such, in global warming.

The laser, known as the Global Ecosystem Dynamics Investigation (GEDI) lidar, the instrument will be the first to systematically probe the depths of the forests from space, and assess how they affect our weather systems and other ecosystems.

Climate change is already upon us, experts say, and we are already feeling its adverse effects in the form of extreme weather events: scorching temperatures leading to droughts, torrential rains causing widespread flooding, and record freezes bringing feet of snow.

But what of the less obvious effects of global warming?

It seems that climate change is impacting life across the whole planet in the most unexpected ways: a new study suggests that the increasing acidification of ocean waters caused by rising atmospheric carbon dioxide levels could rob sharks of their ability to sense the smell of food.

This weekend, hundreds of thousands of people will take to the streets for the People’s Climate March, part of the biggest global protest ever to highlight the issue of climate change.

The march will take place in New York on September 21st, ahead of a major United Nations summit that is bringing together government leaders from around the globe to discuss this global emergency. Satellite marches will also take place in a variety of other locations around the world (see http://peoplesclimate.org/global/ for more details).