<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><span style="font-family:arial,sans-serif">On Sat, Mar 18, 2017 at 10:30 AM, BillK </span><span dir="ltr" style="font-family:arial,sans-serif"><<a href="mailto:pharos@gmail.com" target="_blank">pharos@gmail.com</a>></span><span style="font-family:arial,sans-serif"> wrote:</span><br></div><div class="gmail_extra"><div class="gmail_quote"><br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><span class="gmail-m_-1114618446392194336gmail-m_-6336752058631445019gmail-">
><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">></div> I'm more curious about what would happen to vertebrates and other macrobes<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div></span><span class="gmail-m_-1114618446392194336gmail-m_-6336752058631445019gmail-"> under lunar or Martian gravity, simulated or actual.</span></blockquote><span class="gmail-m_-1114618446392194336gmail-m_-6336752058631445019gmail-"><br>
</span><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">> </div>I thought NASA already knew that?<br></blockquote><div><br></div><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font size="4">How could NASA know that? They know that long term exposure at zero-g is harmful to humans because there is a way to test for that and they have done so, but the only way to know if living for a long time at lunar 1/6 g or at martian 1/3 g is harmful is to send astronauts to the Moon or Mars and have them life there for a long time. Maybe there is a threshold and if the g force is greater than that you're OK, or maybe there is a linear relationship between harm and g force all the way from zero g to 1 g. I rather doubt that last one is true because most things in the universe are not linear,</font></div></div><div> <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">> </div>There is also cosmic ray damage to worry about as Mars and the Moon<br>
has no protection.<br></blockquote><div><br></div><font size="4">We know more about that. As far as radiation exposure is concerned it's pretty clear there is a<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>threshold<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>and it's somewhere around<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>100<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>millisieverts<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>(mSv)<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">. </div>If you're below that figure the radiation has not harmed you, and as likely as not has probably improved your health more than zero milliseverts<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>would have, but if you're well above that figure then you're in trouble, and unfortunately if you're in space you soon get above that figure. </font><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"><br></div></div><font size="4">On the surface of the Earth you get<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>about 2.4<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>mSv<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>per <b>year</b><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>from normal <div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"></div>background radiation, but<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>on the surface of<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>the Moon<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>you'd get<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>1.2<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>mSv<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div> per <b>day</b>,<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> and </div>on surface of Mars you'd get<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>0.7<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>mSv<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>per <b>day</b><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"><b></b></div>. And going as fast as possible with chemical rockets a astronaut would receive 330<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>mSv<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>on the journey before he even set foot on Mars<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">,</div><div class="gmail_default" style="display:inline"><font face="arial, helvetica, sans-serif"> assuming the ship had as much shielding as the Apollo command module.</font></div><br><br><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>John K Clark</font><div><b><br></b></div><div><br></div></div></div></div>