Behind The Black – Robert Zimmerman

A very long (182 pages) and detailed preprint paper was published today on the Los Alamos astro-ph website, describing the completion of a survey of just about all the sunlike stars within approximately 82 light years of the Earth. I haven’t had time to read the whole thing, but the abstract made these notable points:

• The study found that more the fifty percent of all sunlike stars are single stars.
• Among double and triple systems, the bell curve for the orbital periods peaked at 300 years.
• The more heavy elements the star has (atoms more complex than hydrogen and helium), the more likely it will have planets.
• The very intriguing conclusion: “The fraction of planet hosts among single, binary, and multiple systems are statistically indistinguishable, suggesting that planets are as likely to form around single stars as they are around components of binary or multiple systems with sufficiently wide separations. This, along with the preference of long orbital periods among stellar systems, increases the space around stars conducive for planet formation, and perhaps life.” [You need to download the full pdf to see this quote in the unabridged abstract.]

In other words, the evidence continues to suggest that solar systems like ours are very common.

For those who fantasize that Mars might still have vast underground lakes with fish, the recent data is unfortunately not encouraging. A paper published today by the American Geophysical Union suggests that if groundwater exists on Mars, it is going to be increasingly difficult to find, possibly only in the low latitudes at low elevations. These paragraphs from the conclusion of the paper say it all:

Various lines of evidence suggest that at the time of the Late Hesperian, Mars possessed a planetary inventory of water equal to a global ocean ~0.5 km deep, much of which is believed to have been stored as ground ice and groundwater in the subsurface. The potential survival of groundwater to the present-day has important implications for understanding the geological, hydrological and mineralogical evolution of the planet, as well as the potential survival of native Martian life. The two most important factors affecting the persistence of groundwater on Mars are the depth and pore volume of the cryosphere.

To date, the orbital radar sounding data from MARSIS [an instrument on Mars Orbital Express] has provided little evidence of any deep reflectors potentially indicative of subpermafrost groundwater. Here we have examined two (of several) possible explanations for this lack of evidence: (1) that subpermafrost groundwater no longer survives on Mars or (2) that groundwater is present, but that a thicker than expected cryosphere has restricted its occurrence to depths that exceed the estimated ~3 km maximum sounding depth of MARSIS.

[snip]

Which one (or combination) of explanations discussed here is responsible for the lack of deep reflectors on Mars is unknown. But our revised estimates of cryosphere depth suggest that a successful detection of subpermafrost groundwater, outside of those areas on Mars that combine low latitude and low elevation, is unlikely. In an effort to better constrain this problem, a more comprehensive investigation of the MARSIS sounding data obtained over Athabasca Valles, and four other low-elevation, near-equatorial sites, is currently underway.

Tonight, from 9 pm to 1 am (EDT), I will be on the John Batchelor Show. John is off tonight, so the guest host is Simon Constable, with yours truly acting as his co-host. For my part, I’ve arranged four guests:

• Dr. Roy Spencer, climatogist and former NASA scientist, who will discuss the recently published global warming black list as well as other climate change issues.

Then I have brought in three guests to talk about the Obama administration’s new space policy and the space war developing between the administration and Congress over the administration’s effort to cancel the Constellation program:

• Scott “Doc” Horowitz, former astronaut and designer of the Ares rocket. He will offer his reasons for opposing the Obama space proposals.
• Dr. Charles Lurio, space analyst and publisher of the Lurio Report. He will outline reasons to support the Obama proposals.
• Dr. David Livingston, host of the Space Show. He will fill us in on the state of the aerospace community and what it thinks of the Obama proposals.

Each will have his own 15 minute segment to express his views. Should be a fun time tonight.