Nanobacteria are bacteria with sizes in the range from under 1 micrometer to approx. 20 um. 'Normal' bacteria are sized 50 um to 100 um. I substituted to um to avoid character disturbances over the net.
Only a few years ago, scientists thought that no nanobacteria with sizes under 5 um live on Earth. But then a very strange bacteria was found in the Columbia River basalt rocks. They are believed to live far within the rocks (few km), cause they need no light, only water and the surounding basalt rocks to produce methane, their food.

Most of the IMAGES are CLICKABLE !!! 

The bacteria ( look for the 'wire' ) is about 2 um long and 0.1 um thick.

Other Nanobacteria were found in hot springs in Yellowstone National Park. They live within a very extraordinary environment of 85 degC hot water and much sulfur. Imagine their shape like the Columbia River bacteria.

Very extraordinary bacteria exist in the deep ocean, near so called 'black smokers'. This are very little 'vulcanos' with sulfur-water outlets. Those bacteria live without sunlight and oxygene, only by 'eating' sulfurhydrogen at a temperature over 80 deg.C.

Very hot new discoveries come from the Russian Antarctic Station Vostok. They take probes of the permanent ice core since the 70s and nowadays a depth of 2900 meters is reached. Measured are CO2 (carbon dioxide), CH4 (methane) and dust within the ice to determine ancient climate. CO2 and CH4 are major factors for the global temperature, so precises information of cold and warm periods are the result. The Nanobacteria, photographed with a electron-microscope of Marshall Space Flight Center, have very exotic shapes as seen below. 

Temporarily named Klingon. Size ~ 12 um.	Part of the colony named  Mickey Mouse. Size ~ 1 um.	Temporarily named Sphere.  Size ~ 15 um.

More detail will follow when released.

But now to the question since centuries. Is there life outside our Earth ???

In 1984 the Martian Meteorite ALH84001 was found at Allen Hills / Antarctica. Years of investigation and photographing with a electron microscope brought out fantastic results. Scientists found evidences for life. 

Similar yellow / orange areas are found on Earth, left by bacteria. One may say that the metoerite was contaminated after the impact on Earth, 13000 years ago, but the density of these areas increases to the center. If it was contaminated it would be vice versa.

This colony was found deep in the meteorite.	This 'space-worm' is about 1 um in length,  similar to the Columbia River 'thingie'.

Since 1996 the NASA has started a massive Mars program, starting with Mars Observer (Orbiter ; lost at orbit insertion), then Mars Pathfinder (Lander) which was a major success, Mars Global Surveyor (Orbiter ; which is now is in orbit) and end of 1998 Surveyor 98 (Orbiter and Lander) is launched to search for water and life.
But ALH84001 was not a Sample Return Mission, it was thrown out of Mars athmosphere by a impact of an asteroid and had enough energy to leave martian orbit. After a journey of several million years thru our solar system it impacted on Earth.

In case of finding bacteria frozen in Antarctica, we have to look to other places in our solar system where similar conditions exist e.g. Jupiter moon Europa (ice core) and Comets (consistance mostly of waterice).

(C) 1998 Captain !