In August 2008, NASA confirmed water on the planet Mars.

They have analysed Martian soil samples gathered by the Pheonix lander, from the surface of Mars.

How is this done from so far away, you may wonder?

Astonishingly, Pheonix has a robotic arm. It is able to reach out and scoop red soil from the Martian surface, into the spacecraft’s body. There, the soil is heated and the vapours analysed.

Water has been confirmed. It has been suspected for centuries, but only now “touched and tasted” in the words of the scientists involved.

The question of water on Mars, became a full-blown controversy in the late 1800’s.

Leading astronomers notably Percival Lowell, claimed to have observed networks of “canals”, through telescopes. Previously, they had been suggested by Shiaparelli and termed “canali”.

Quickly, it was speculated they were the work of intelligent beings – hence the notion of “Life on Mars”. Water is a prerequisite for life as we know it.

In 1898, the publication of H G Wells’ famous novel “The War of the Worlds”, added populist fuel to the debate.

Perhaps this latest discovery from NASA of water evidence, will rekindle the speculation? I’m sure, further work is needed for any proof.

Neptune is the furthest out of the “Gas Giant” planets and is right out at the limits of our Solar System, 2800 million miles from the Sun.

The story of its discovery is fascinating…

Neptune

Neptune’s existence was suspected long before it was actually discovered.

Astronomers in the early 1800’s found that they could not reconcile the observed position of the newly discovered planet Uranus, with the position they expected through calculations.

So some astronomers began to suggest that perhaps there was an undiscovered planet in the same area of the Solar System, that was affecting the orbit of Uranus.

Various people became involved in the search for the new planet. Notably, these included a young French mathematician called Urbain Le Verrier and a young English mathematician called John Couch Adams.

Both of these men calculated where in the sky, they would expect Neptune to be found. Adams did not publish his work, but Le Verrier did by means of two notes, in 1845 and 1846.

The search to find Neptune observationally began.

John Challis, Professor of Astronomy at Cambridge, used the Northumberland 11.6 inch refractor but did not find it.

(Incidentally, this telescope can be visited and is still used at the present time, in Cambridge. I have seen it and it is a wonderful piece of astronomy history)

Reviewing the episode later, after the new planet had been discovered, Challis found that he had actually seen and recorded Neptune almost immediately in the predicted position, but he had not realised it. I bet he was cross!

Meanwhile, Le Verrier had sent his calculations and predictions to Johann Galle at the Berlin Observatory.

With this valuable information, Galle looked and found very quickly. Neptune was discovered on his first night’s observation in 1846.

Later, it was discovered that Adams had also been correct with his predictions of Neptune’s position, but unfortunately, it had just taken too long for the English astronomers to follow it through to the observation stage.

Neptune is not actually that difficult to see with a telescope, if you know where to look and what you are looking for.

Through a telescope, the Neptune’s disk looks blue. Like Uranus, this is due to light absorption by methane.

Neptune is also very similar in size to Uranus.

The largest of Neptune’s moons, Triton was discovered soon after the planet itself in 1849, but the second moon, Nereid, took much longer (1949). It is close to the planet and hard to see.

The most significant recent event was the Voyager space mission. It flew past Neptune in 1989.

Voyager found six additional satellite moons, together with a faint ring system – another similarity with Uranus.

However Neptune does not share Uranus’ extreme axial tilt. Neptune’s axis is inclined at just 29 degrees to the plane of the orbit. Only a few degrees more tilted than Earth.

Voyager also succeeded in measuring the period of rotation. Neptune’s “day” was found to be 16 hours 7 minutes long.