The year 2008 will be a year of 50th anniversaries for space exploration. Following in the wake of Sputnik I and Sputnik II, on January 31, 1958 the United States launched Explorer 1.
A recent conference on the moons of Mars reminded me of the wonders that await us even in our own solar system.
Galileo represented a new phase in the study of the outer planets. Pioneer and Voyagers 1 and 2 together completed the preliminary reconnaissance of those gas giants, but Galileo undertook a much more systematic, in-depth and holistic analysis of the entire Jupiter system.
Originally planned to explore the gas giant planets and their satellites, the Voyager spacecraft have continued their journeys and are now the most distant human objects in the cosmos.
The recent award of the Nobel Prize in Physics to NASA astrophysicist John Mather and University of California Berkeley astrophysicist George Smoot reminds us that NASA not only undertakes voyages in space, but also in time.
The universe is what it is, not what we want it to be, and science must always be open to correcting its mistakes.
Less than a century ago, the planet Venus was most often referred to as "Earth's sister planet."
Exploration doesn't happen by sitting still, physically or intellectually.
No single essay can do justice to the events that took place between 1968 and 1972, four years that, as time passes, seem all the more remarkable for human history.
It is hardly cause for surprise that with the beginning of the Space Age humans set their sights on the nearest celestial body, the Moon.
Daring though voyages to comets have been, with comet material often pelting and even damaging passing spacecraft, voyages to asteroids have gone one step further, achieving an actual landing, or maybe two landings.
Among the more adventurous voyages of exploration are those whose destinations are comets.
Humanity's epic voyages to the Moon are well known, the stuff of history. But what about voyages to the Sun?
In October 1995 - ten years ago this month - two Swiss astronomers announced the discovery of the first planet around a Sun-like star outside of our solar system.
Exploration is necessary for a creative society and risk is the inevitable companion of exploration.
The study of cosmic evolution allows us to see the universe as it really is, to reflect on our place in it, and to "know the place for the first time."
Why do we explore? Since the beginning of the Space Age one of the chief drivers has been the search for life beyond Earth.
Human exploration is more than the sum of all science.
One of the benefits of space exploration is international cooperation.
As controversies swirl about funding, resources, motives and methods for spaceflight, it is well to consider the consequences of exploring space – and of choosing not to do so.