In a little over 12 hours time, the latest Mars Science Laboratory, and the Mars Rover Curiosity, will perform the most difficult and risky sequence of events of the mission to date - to effect a safe landing and deployment of the probe on the surface of Mars.
The 7 minute descent manoeuvre, and the 14 minute delay in communications between Mars and Earth - mean that it will be a very tense 14 minutes for all those following the mission - and the staff of the Jet Propulsion Labs in Pasadena, California. This video 7 minutes of Terror, gives a good illustration of what the final descent and landing involves.
So far, of all the Mars surface probes launched, there has only been a 40% success rate of safely landing. Lets hope that the $2.5 billion Curiosity bucks the trend, has a safe descent, and does not become the latest member of the exclusive Mars "Crash and Burn" club.
Space Exploration, or any kind of exploration, carries with it certain risk. The early Explorers of the New World, faced numerous perils, not to mention the arduous sea journey with the risk of shipwreck, disease, pirates or unfriendly natives.
I have recently finished reading an excellent history of San Francisco, which covers the 1830s to 1906, the Gold Rush and Boom Town years right up to the earthquake and its aftermath. It is fascinating that in the 1840s, San Francisco was little more than a village of 500, and by 1852, as a result of the Gold Rush was almost 35,000.
Getting to California in the 1850s was a dangerous and long journey. For the European, the journey could be over a year, by boat via the Isthmus of Panama, or the considerably longer journey around the Cape Horn. For those that set out by wagon trail across the Mid-West, the perils of the Sierra mountains, often resulting in starvation and death by exhaustion - it was estimated that those who made it to 1850s San Francisco disease due to poor sanitation, overcrowding and violent crime 20% were dead within 6 months.
Compare this with modern long haul air travel, where we spend 12 hours in a 747, and the only discomforts we face are to moan about the food, the size of the seat and the disappointing choice of movies.
Having crossed the Atlantic four return times in the last 12 months, and peered out over the Sierras from 35,000 feet, it is hard to imagine what our forefathers endured, to fulfill their basic instinct of human curiosity.