MESSENGER orbit insertion maneuver (OIM), which was to be the first time any spacecraft has ever orbited the planet Mercury. It was a critical moment for the mission -- perhaps the most critical of its 6 1/2 years in flight -- and there was only one chance to get it right. Had the OIM burn failed, the spacecraft would have whizzed by Mercury, perhaps never to return. Fortunately, the maneuver seems to have been a total success.
NASA television is pretty cool, really. Their budget is clearly not incredibly high, but there are no commercials at all, and you get to enjoy an unfiltered look at our space operations. There was, of course, no live television images broadcast from MESSENGER, so the coverage consisted of interviews, animations, slide shows, and a live feed from mission control. It was all I needed to be content for the evening.
The last time Mercury was visited by any spacecraft was in 1975, when the Mariner 10 spacecraft made the last of its 3 flybys. Mercury is too close to the Sun to be observed by the Hubble telescope, so if we want to get a good look at it, we have to send a spacecraft. But because it orbits in such a hostile region of space, any spacecraft bound for Mercury must be engineered to deal with extreme temperature fluctuations; there is an almost 1100 degree Fahrenheit difference between light and shadow. Mariner 10 provided us with a lot of great science... among other things, it discovered that Mercury has a magnetosphere, totally unexpected amongst astronomers. But due to the timing of its flybys, and the nature of Mercury's slow axial rotation, it was only able to photograph about 45% percent of the surface of Mercury. The rest would remain a mystery. There would have to be another mission -- an orbital mission -- to map the rest of the planet, and answer some of the questions that were raised by the tantalizing results of Mariner 10.
Friday, March 18, 2011
Friday, March 4, 2011
There are a variety of alternative theories put forth by the skeptics in this camp. Sunspots and sun cycles have been blamed for global warming, as have volcanic eruptions, cosmic rays, and various other astronomical causes (variations in Earth's axial tilt, the fluctuating eccentricity of Earth's orbit and the precession of equinoxes as relates to perihelion and aphelion, for instance). Now, there is no question that these various factors do affect Earth's climate, and that can be seen clearly in the record of ancient climates. We know that the Earth has seen periods of natural warming and cooling, and there is no doubt that these sorts of changes will happen again. Nevertheless, these variables cannot explain the warming trend over the last 100 years or so nearly as well as anthropogenic factors, like the emission of enormous levels of carbon dioxide corresponding to the industrial revolution.
Skeptics of mainstream climate change theory may take to these other hypotheses in part because there is a sense that we humans are not capable of making big changes in our ecosystem. Of course, history tells us otherwise. Human beings have driven many species to extinction or to the brink of extinction by over-hunting and habitat destruction, and in the 20th century, with the advent of chlorofluorocarbons (CFCs), we put an enormous hole in our ozone layer. Meanwhile, we continue to possess the power to cause a global nuclear winter.
To understand how humans are capable of making such profound changes to the climate, we have to understand the two main elements behind our increased impact on the environment: the industrial revolution and recent population expansion.