While Chris is correct that no one is claiming daily arrivals of Martian meteorites, the possibility that Martian meteorites reach Earth regularly and could serve as a viable mode of transport for micro-organisms is well supported.

<a
href="http://www.planetary.org/html/news/articlearchive/headlines/2000/swapp
ingrocks.html"> Swapping Rocks: Exchange of Surface Material Among the
Planets
<a
href="http://www.planetary.org/html/news/articlearchive/headlines/2000/Pansp
ermia.htm"> Life From Space? Testing Panspermia With Martian Meteorite
ALH84001
Surviving Space: How Bugs Might Travel Between Planets
<a
href="http://www.space.com/scienceastronomy/solarsystem/mars_knocks_021107.h
tml"> Why a Mars Rock Hits Earth Every Month
Life's Rocky Road Between Worlds
Hitchhiking on a Meteorite: Is there Mars Life on Earth?
Bugs could travel in comfort aboard meteorites

The fact that all three PR replies to Zubrin ignored this issue while pointing out some valid reasons for taking precautions is a major error that Zubrin pointed out in a rebuttal Robert Zubrin Responds. Rummel's reply is so short on detail that he admits skipping, it is more an apparent case of turf protectionism than rebuttal. Most of the article simply states the obvious and does not actually contradict Zubrin. His main contradictory comments have little support. The fairest and most accurate reply (while still avoiding the meteorite issue) was made by Kenneth H. Nealson (Practice Safe Science) who quite accurately noted:

"I (and most biologists) would (and do) agree with some of his statements. For example, the likelihood of life on Mars is small, and the likelihood of more advanced, mammalian-like life is even smaller. Moreover, the likelihood that a Mars organism pathogenic to Earth life exists and that, if it did, it could compete with highly adapted and competitive life on Earth is very small. None of this is new-it is comprehensively reviewed and discussed (with proper citations) in a National Research Council report ("Mars Sample Return: Issues and Recommendations," Washington, DC: National Academy Press, 1997). This report, produced by actual experts, visits virtually all of the issues brought up by Zubrin and is, in fact, in general agreement with many of his statements."

He starts however by making questionable statements about Zubrin's expertise acting as if Zubrin knows no experts on the issue despite well known association with Martian exobiology experts for decades and goes on to state "the problem is that Zubrin selectively ignores other facts and takes things out of context. For example, the following cannot be ignored" while glaringly ignoring the meteorite issue. The specific items were:

1) None of the unlikely events discussed in the above paragraph can be shown to have a probability of zero. (Accurate)

2) If the probability isn't zero, the potential risk is very high (only if we do not take precautions).

Blatantly inaccurate. A low probability event is considered low risk in hazard assessments unless the nonzero hazard is extreme. In laymen's terms multiply the probability of the event occurring by the expected number of deaths if it occurs to determine the relative risk compared to other accepted risks. Extra consideration is of course given if the potential number of deaths is very high. According to the overall panel of experts who have reviewed this issue at Mars Sample Return Issues & Recommendations there is little reason to believe Martian life will be hazardous if it exists. Claiming the risk is high has no basis in fact. Far less basis in fact than Zubrin's often criticized Dutch elm example

3) The public will not be swayed by the bluster of science (with no data) or any "Trust me, everything is going to be OK" arguments. (Accurate)

4) The samples will need to be protected from the Earth-contaminating them would truly be viewed as a "crime against science." It would therefore seem prudent to include in any relevant mission the technology to ensure that samples will be contained.

Accurate in content but inaccurate in rebuttal as Zubrin point was irrational mission constraints due to the threat of back contamination not ignoring good scientific protocol. This was made clear in Zubrin's rebuttal Robert Zubrin Responds:

"Everyone agrees that measures should be taken to preserve the scientific value of the Mars sample. The issue is whether foundationless fears should be allowed to distort mission design so as to increase the chance of failure. NASA lost two Ranger lunar missions as a result of completely pointless spacecraft sterilization measures demanded by the planetary protection folks. As a result of their demands, in 1998 the Jet Propulsion Lab adopted a mission protocol for the Mars Sample Return stating that if a signal confirming sample confinement were lost from a returning sample craft, the return vehicle would be directed to bypass Earth.

We have already spent two decades planning a Mars Sample Return mission, and it's likely we'll spend at least another. Before we're done, at least a billion dollars will have been spent in an effort to get a sample from Mars. Yet the back contamination worthies argue that all that time, effort, money, talent, and potential for discovery should be tossed like garbage to appease tabloid fears over a nonexistent menace."

5) Technology for protecting samples and containing potential biohazards is not at all out of reach. The containment and shipping of samples known to be dangerous is routine. Moreover, the technology is adaptable and appropriate for the kinds of sample materials anticipated from Mars.

Again accurate in content but again inaccurate in rebuttal. Zubrin was not calling for no protective measures. He specifically mentioned the need to keep samples pristine for scientific reasons in his rebuttal. His prime issues were aborting the mission in event of failure and overloading the mission with protective measures out of proportion to the risk. All three authors seemed to respond more to Zubrin's title and opening paragraphs rather than the entire content.

The other reply to Zubrin by M. Race was at Hazardous Until Proven Otherwise

Regards,
Mark Eby