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Eternal clear skies, but brace for thermal whiplash

Dr Emily Baldwin

It is another day of zero wind, zero clouds, and zero rain here on Earth’s Moon, but there is a one hundred percent chance of thermal whiplash as temperatures swing several hundred degrees between sunlight and shade. Be sure to wear your full protective suit and boots at all times as you step between blistering hot regolith on the baking plains and the cryogenic cold cast by a shadowy crater wall. Reflective visors are mandatory. Regularly douse your suit in SPF 5000 to reduce damage by the unfiltered solar radiation.

While the general outlook is a highly predictable two weeks of searing heat followed by two weeks of brutal cold, let us take a look at the regional forecast:

Expect lovely clear conditions at the equatorial maria with highs of around 120º Celsius at local noon. Picnics are discouraged, however, on account of unprotected foodstuffs rapidly boiling away into vacuum and the continuous micrometeorite rain adding unpalatable grit. By nightfall, temperatures may plummet below –170ºC.

At the poles, the Sun will be hovering near the horizon. For those looking for a more stable climate, the polar regions offer both permanently shadowed zones and perpetually sunlit ‘islands’ – perfect for sun-seekers and shade-bathers alike. Expect balmy temperatures between –20 and 54ºC at the ever-popular ‘peaks of eternal sunshine’ along the rims of Shackleton Crater at the South Pole, and Peary Crater at the North Pole. The poetically named peaks see the Sun 70–95% of the year. But while it may sound idyllic, expect crowds and eyesores: they are hotspots for installing solar power generators.

Cold-climate explorers will enjoy the attraction of permanently shadowed polar craters; temperatures barely rise above –230º Celsius in the deepest pits. While hidden pockets of billion-year-old ice may result in slippery surface conditions, with the right equipment you may be able to extract water suitable for drinking, oxygen for your breathing apparatus, and even hydrogen for your return rocket ride home.

Radio astronomers will delight in the lunar far side being shielded from Earth’s radio noise, and with absolutely brilliant seeing conditions for astronomers every single night (on account of there being virtually no atmosphere, only the thinnest covering of gases known as an exosphere), book your astro-holiday early to avoid disappointment.

On a day-to-day basis and across the globe, expect the usual light sprinkling of helium, neon and argon, with trace amounts of other elements, including hydrogen and sodium, creating a light haze in the tenuous exosphere. The dust index remains exceptionally high – always give your suits and vehicles a thorough scrub to decontaminate them after use and to avoid clogging. And be sure to check the solar activity forecast each day: seek cover underground (check the emergency lava tube refuge map for your region) or remain inside your habitat if a solar storm is headed your way. Enjoy those clear skies in the meantime!

Dr Emily Baldwin is Astronomy Now’s Digital Content Manager.

Hike the lunar poles

Earth-based lunar observers can enjoy a visual hike around the Moon’s poles – refer to Moonwatch in the January and February issues of Astronomy Now for your two-part expedition guide!

Read more

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