A hole in Mars
The mysterious black spot in this picture is the entrance to a cave on the surface of Mars.
About 130 yards across, the size of a football field, it is one of seven cave entrances near the volcano Arsia Mons in the southern region of the Red Planet.
The caves may be interconnected, and may prove to be the abode of bacterial life. Some caves on Earth, even in the most inhospitable environments, are full of such life forms.
The two-mile deep Mponeng gold mine in South Africa has walls filled with ancient water that is millions of years old which are alive with microbes.
The interiors of Martian caves are likely to be much warmer and therefore much more conducive to life than the planet's frigid surface.
Like the ancient lava caves on the surface of the Moon, they may also one day be suitable for human dwelling?certainly a much cheaper project than constructing a habitat.
Traversing the Summer Triangle is the small but interesting constellation of Vulpecula the Fox. It contains the beautiful Dumbbell Nebula (M27), a planetary nebula, so called because it vaguely resembles a planet in appearance, but is in reality the relic of a long-vanished star.
Just to the east of M27 is a star with a fascinating planet, only discovered in 2005. The star HD 189773 A is a yellow dwarf, meaning that it is like the Sun only redder.
In extremely close orbit round it is a planet about a tenth more massive than Jupiter that orbits every two days, nearly 2,000 times faster than Jupiter which takes only 12 years go round the Sun. Stranger still, it is only three million miles from its parent sun (compared with Earth's 93 million), creating a world far too hot to support any kind of imaginable life.
South of Vulpecula is the small but distinctive constellation of Sagitta the Arrow, on the east side of the summer Milky Way. Its shape really does resemble an arrow, with its four main stars in a roughly straight line.
Many civilisations have indeed seen Sagitta as an arrow, and it is said to have been shot by Hercules in his Sixth Labour at the Stymphalian birds with their claws, beaks and wings of iron who lived on human flesh in the marshes of Arcadia.
Of particular beauty is the rich globular cluster M71, between the stars Delta and Gamma Sagittae. In low magnification it appears as a somewhat bluish star.
At a distance of about 18,000 light-years, it consists of many stars with a densely star-packed region of the Milky Way in the background.
And to the south of these two constellations is Altair, appropriately called the King of Birds, in the constellation of Aquila the Eagle. It is one of the most brilliant of all stars, the southernmost member of the great triangle.
Although only 16.6 light-years away, little is known of it. It rotates so fast that it must have the shape of an egg.
Of local events, Mars rises at about midnight in Taurus, two minutes earlier each night. Jupiter sets low in the south-west, about two hours after the Sun.
The other planets cannot be easily be seen.
Visit Adrian Berry's website at www.adrianberry.net
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