Podcaster: Frances McCarthy
Title : What Is The Stars – MESSENGER at Mercury
Organization: CIT Blackrock Castle Observatory for ‘The Blue of the Night’on RTÉ Lyric FM, copyright RTEì Lyric FM
Description: The Fermi Paradox: Given the size and age of the universe there should be extra terrestrial life but how come we can find no sign of it.
Produced by Eoin O’Kelly for The Blue of the Night on Raidió Teilifís Éireann’s RTÉ Lyric FM. From April 16, 2012.
What is the Stars was originally broadcast weekly between 2010 and 2012 on ‘The Blue of the Night,’ RTÉ Lyric’s evening radio programme. It was aimed at a “thinking-adult-late-evening audience.” Broadcasts were planned to be topical, yet with a spacey/astronomical theme. Scripts were written and delivered by Frances McCarthy of CIT Blackrock Castle Observatory, Cork, Ireland. Frances completed a BSc in Physics and Astronomy from the University of Toronto before exoplanets had been confirmed and still cherishes the two pieces of fan-email she received from listeners!
What is the Stars is a line from The Plough & the Stars, a play by the Irish writer Seán O’Casey.
Bio: Frances McCarthy, astronomer and education officer at Cork Institute of Technology’s Blackrock Castle Observatory guides our eyes heavenwards to explore the myths, stories and science of the constellations.
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Mercury is one of the trickiest planets to see, often being so close to the horizon from Ireland that it just can’t be clearly seen. But, we do have another way to gather data from this planet.
The one year primary mission has just ended, but it has had its funding extended for one more year – which is three years on Mercury. The next year will see the spacecraft change its orbit to be closer to the planet for longer periods. A further extension will not be possible – the spacecraft does not have enough fuel to maintain its orbit and will crash into the planet a few years later.
Think of Mercury as a metal ball a bit larger than our Moon, with a rocky crust on top. The dense metal core must be partially liquid – given that Mercury has a magnetic field – albeit only 1% of the Earth’s field. The core is huge for the size of the planet – it’s now reckoned to be 85% of the planet’s radius (compared to the Earth’s 55%), and this led to some unusual models of how this planet formed and where the rest of it went. Perhaps it was hit by a large object when it was newly formed and this led it to lose much of its mass, or perhaps the Sun gradually stripped off the more volatile elements from its outer layers? The latest data from MESSENGER shows that both of those ideas are wrong. The planet’s geology bears a closer resemblance to meteorites than its rocky neighbours, so current models of its formation will have to be reworked. As one of the project scientists pointed out:
“It’s the anchor at one end of the Solar System. Learning how Mercury formed will have major implications for the rest of the planets.”
Besides a shake up on ideas of the planet’s formation, new images of the surface have revealed that the surface of Mercury seems to still be active. Bright and blue depressions, dubbed “hollows,” seem to be younger than the craters that they are found in – and they occur all over Mercury. It had been thought that Mercury was a static world – with no atmosphere or volcanic activity, the only thing that would affect the surface would be impacts. One theory about the hollows suggests that they may have been formed when material from the interior of Mercury was forced up and exposed to space after an impact. Material like sulphur could have escaped, perhaps leaving a fragile rock surface that would have collapsed down on itself. There are similar depressions in the polar ice of Mars, but they have never been seen in a rocky surface before.
And talking about ice – it is believed that the permanently shaded craters at the poles of Mercury might hold ice, shadowed from the Sun’s glare. The high resolution maps of the poles show that the reflective radar areas that have been detected from Earth match up with the shadows found in craters, which is supportive of the idea that ice is lurking in these cold traps!
End of podcast:
365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by Planetary Science Institute. Audio post-production by Richard Drumm. Bandwidth donated by libsyn.com and wizzard media. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. This year we will celebrates the Year of Everyday Astronomers as we embrace Amateur Astronomer contributions and the importance of citizen science. Join us and share your story. Until tomorrow! Goodbye!