NASA's Messenger has delivered its second set of postcards from Mercury, following a successful low-altitude fly-past on Monday which saw the spacecraft swoop to within 125 miles (200km) of the planet's surface, snapping furiously as it went: Messenger view of Mercury. Pic: NASA This image was taken around 90 minutes after …
Looks very pockmarked
I thought that, with Mercury being so close to the Sun, there would be a lot fewer, or even no craters than that. Doesn't the surface get regularly melted, or even permanently on the 'sun-facing' portion of the surface. We can quite clearly see a lot of old craters on there . . .
@Looks very pockmarked
Au contraire! - The hottest planet in the solar system is actually Venus, because of its runaway greenhouse effect. Mercury, being much smaller, and so close to the sun, has had any atmosphere stripped away by the solar wind so cannot suffer the same fate. Still, it's a bit warmer than you or I would find comfortable but nowhere near hot enough to melt most types of rock.
Surface temperatures vary between 90-700 K - hot enough to melt some soft metals, but nowhere near enough to melt rock. Mercury was thought to be tidally locked to the Sun (as the moon is to the Earth), but we now know that it is actually in a ratio of 3:2, so a solar day on Mercury lasts for two local years (2 x 88 days).
Mercury does get VERY hot in the midday Sun, but it also gets VERY cold in the middle of the night. There's no atmosphere to balance temperatures, so the range is extraordinary.
Mercury also has probably not had any significant tectonic activity for a few billion years. It's a small planet so it has a high surface to volume ratio and radiated its internal store of heat into space a long time ago. There's some conflicting evidence whether any of Mercury's interior is molten or in a plastic condition, but if it ever had plate tectonics they grated to a halt in the early days of the Solar System.
With no tectonics and no atmosphere, Mercury's surface preserves features for millions, if not billions of years. Many of these craters are probably a similar age to those on the Moon and date from around 4 billion years ago. The very bright craters are relatively recent - say in the last billion years; they're bright because of the freshly-broken ejected material splashed over the surrounding terrain. They're gradually eroded by micrometeorite bombardment and the impact of solar particles.
Now what would be interesting is if we found ANY signs of recent vulcanism. Many experienced telescopic observers have seen temporary patches of brightness and light on the Moon which have been called transient lunar phenomena and might be dust or gas erupting from the deep interior. Mercury, being more massive, should be hotter inside and might even have patches of molten material finding their way to the surface.
Here for all to see is the evidence that technology, plus a will to achieve, can survive the most stringent tests. The images are outstanding! Such a wealth of information is surely an invitation to further exploration and study. I sincerely hope and trust that future discoveries and disclosures will never be suppressed or diluted by mere money-grabbing, quick-profit interests who aren’t interested in anything other than their short-term profit margins.
I smile at Mercury’s 25MHz processors and 10MHz support systems and remember what spectacular achievements were made a decade or two ago (yes, I did my bit – no pun intended). I wonder at what we are really doing with our current multi-GHz systems today. I can only thank the current generation of computing systems and their programmers for their ability to process the data so quickly and efficiently. It’s a pity that so many millions of relatively powerful computing systems are used simply for entertainment and emails.
The achievements of all the systems plus at least the concept, design, development, planning, management, funding, production and delivery mechanisms cannot be overlooked. For a project to deliver delicate scientific equipment to such a lethal environment is a triumph. Let’s keep the networks open and guard against any and all attempts to throttle the resources and communication infrastructures we now have - and those we will have in time to come. Long Live Moore’s Law I say.
I feel a little ignorant for not knowing this but why are all these fly-by pictures in black and white? They are fascinating but I'd love to seem them in colour.
Paris because I'd like to fly-by and probe her...
I believe they are in colour as the images on the site show earth in colour and this image has text indicating that it is in colour: