News Roundup: Ice from the Ashes

martian ice gif animation

Sent by: Phoenix | From: Mars | Credit: NASA/JPL/UA | Image source

Remember the friendly wager we had about the mysterious white substance that Phoenix dug up? And the winner is: water ice. Pictures taken during the past few days show dice-sized chunks of material simply disappearing. (See the lower left corner of the trench in the animation above.) Mars explorers are convinced this was ice that sublimated (turned directly from a solid into vapor) once it was exposed to the open air.

NASA quotes Phoenix Principal Investigator Peter Smith as saying, “It must be ice. These little clumps completely disappearing over the course of a few days, that is perfect evidence that it’s ice. There had been some question whether the bright material was salt. Salt can’t do that.”

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In other robotic space exploration news this week:

  • Epoxi (the spacecraft formerly known as Deep Impact) fired its engine today, setting up a trajectory that will take the craft to comet Hartley 2 in November of 2010.
  • The latest Carnival of Space is now online, offering fresh space links from all over the web.
  • New Horizons, on the second leg of its decade-long odyssey to Pluto, passed the orbit of Saturn. It was the first spacecraft to do so in almost three decades. The robotic ship itself didn’t notice—it continues to slumber in deep electronic sleep as it waits out the long journey.
  • The private space race is heating up.
  • Get more daily reports on the news page.


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While I’m hoping for water on Mars, I’m not getting overly excited about this revelation. From what I’ve read the temperature where Phoenix rests is just above the freezing point of CO2 and still many many many tens of degrees below the freezing point of water. The boiling (sublimation) point of CO2 is approximately −78 °C (195 K) at one earth atmosphere. Given the 1/100th atmosphere of Mars, CO2 would rapidly sublimate when the insulating layer of dust is scraped away exposing it to sunlight and high(er) but still damn cold temperature. My vote is for CO2 melting, sublimating or otherwise vanishing right in front of our eyes. Water ice would take very much longer to do a disappearing act in this incredibly frigid yet evocative series of photos. That is my story and I’m sticking with it.

But I do so wish to be proven wrong.

In the press conference that accompanied the announcement, the mission scientists said they could confidently rule out CO2 ice because the temperatures are currently too warm to sustain it for as long as the chunks lasted, while water ice would be expected to sublimate at just the rate we saw here.

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