Watch out Phoenix! Don’t Scratch the CD!

I’ve just written an article over on the Universe Today about the stunning discovery that Mars regolith actually bears very close resemblance to terrestrial soil. This is very cool as this shows Mars may be capable of sustaining life (as we know it) and it has implications for the future of manned Mars missions (we might be able to use this mineral-rich soil for growing plants for instance). So rather than replicating the article here, I urge you to pop over to the Universe Today article (Phoenix: Mars Soil Can Support Life) and enjoy (I was quite proud of pointing out the huge difference between “soil” and “regolith” in the final paragraph!). But that’s not the point of this Astroengine post, I have a far more pressing issue to voice…

The Phoenix Mars lander has a CD attached to its deck. It’s not your average run-of-the-mill CD though, it’s actually one of the most advanced DVDs ever manufactured. It contains a vast number of literary, visual and audio science fiction works about the Red Planet including 161 novels and stories, 63 pieces of artwork and four radio broadcasts related to Mars. The library totals over 1.43 GB of data. For the full play list, have a look at the Space.com article about the “Visions of Mars” DVD.

According to NASA, the DVD is has its data stored in a robust silicon glass disk, designed to withstand extreme temperatures and freezing carbon dioxide damage. According to the scientist that oversaw the DVDs construction, it should remain undamaged for 500 years. When attached to the spacecraft before launch, the DVD was even baked to remove any explosive CO₂ bubbles. Sounds like an impressive piece of kit.

However, I can see a possible design flaw. As an avid collector of music CDs and data DVDs for computing and films, I’ve often experienced frustrating scratches forming inexplicably on the laser-reading side of my CDs and DVDs. Even disks slid out of harms way inside a protective case have formed small abrasive marks and sometimes corruptible scratches. I remember my treasured limited edition gold-plated Enigma CD succumbing to a nasty score right through the middle. No matter how careful I was, scratches would appear (having said that, I’m surprised most of my collection is still functioning after the chaos of eight years in university digs!).

Back to the “Visions of Mars”. This treasured DVD, apparently the most expensive DVD ever manufactured sits proud on the topside of the Phoenix lander. We often see it as the onboard camera takes shots of the surrounding vista. It is attached to the deck of the lander with Velcro, for easy removal by future Mars colonists so they can have a snapshot view of their ancestor’s thoughts of what Mars means to us. Although it is billed as “indestructible” I was drawn to the most recent photograph to come from the lander (pictured top). The DVD is situated very close to a TEGA oven and MECA wet-lab where the robotic arm drops samples of regolith. Spillage happens (again, memories of university life flood back to me) and a large quantity of dirt appears to have landed next to and on top of the precious DVD.

Assuming the DVD’s only protection is its own hi-tech material, what’s to stop these abrasive grains of rock particles slipping under the disk? There is likely to be some small-scale movement/vibrations on the lander from its own operations, thermal expansion/contraction and the possibility of geological tremors during the lifetime of Phoenix, so could these small grains act like sandpaper against the DVD’s smooth underbelly?

Imagine you’ve settled on Mars and you set out to the Phoenix landing site to retrieve the DVD in, say, 100 years time only to find the DVD has had its transparent underside scrubbed away. That would be a real shame considering you were looking forward to listening to the ancient version of H.G. Wells’ “War of the Worlds” (now that would be cool, late night on Mars, hearing the War of the Worlds soundtrack echo throughout the settlement corridors. Da Da daaaa…)

Anyhow, not a huge issue, but an issue worth sharing (I think) 😉