Venus has the densest atmosphere of the terrestrial planets, consisting mostly of carbon dioxide, and the atmospheric pressure at the planet’s surface is 90 times that of the Earth.

Around each first quarter moon and last quarter moon – when the sun and moon are at a right angle to Earth – the range between high and low tides is least.

Mercury is very hard to observe from Earth because: it never gets more than 28 degrees from the Sun’s glare. From Earth, due to their motions and the fact that the Sun lights only a portion of each surface, both Mercury and the Moon: appear to go through phases.

How does the magnetic tilt of Jupiter compare with our field? Both are tilted about 10 degrees, but Jupiter is opposite in polarity. What is thought to be the cause of Io’s volcanoes? Which of the Galilean moons is the densest and most geologically active?

Mars is known as the Red Planet. It is red because the soil looks like rusty iron.

It is widely accepted that Mars had abundant water very early in its history, but all large areas of liquid water have since disappeared.

radiodurans can survive the harsh ionizing and ultra-violet radiation of space, as well as extreme cold, vacuum conditions, and oxidative damage. Of the three bacteria, the extremophile D. radiodurans would seem to be the most likely analog for life on Europa.

From Earth, through a small telescope or strong binoculars, they look like tiny starlike pinpricks of light. If a moon is in front of the planet, you can sometimes see the moon’s shadow on Jupiter’s cloudtops. Going from closest moon to Jupiter to the outermost, their order is Io, Europa, Ganymede and Callisto.

628.3 million km

The startling colour is due to contaminating minerals rising from beneath the icy crust, possibly salts from the underground ocean. The regions of mottled red are chaotic terrain, parts of the moon’s surface with disrupted icy material that has been broken and shifted around.

Europa is the smallest of the four but it is one of the more intriguing satellites. The surface of Europa is frozen, covered with a layer of ice, but scientists think there is an ocean beneath the surface. The icy surface also makes the moon one of the most reflective in the solar system.

1.315 m/s²