confirm life or its absence on Mars?
The two sophisticated sets of soil analyzers aboard the Mars
Phoenix Lander are trying their hardest and currently, MECA,
which stands for Microscopy, Electrochemistry and Conductivity Analyzer, has
the lead. MECA
is a sensor-based wet chemistry laboratory (nicknamed WCL, pronounced "wickel") that
has twice indicated the surprising discovery of perchlorate salts on The Red
Planet. So far, TEGA
(Thermal and Evolved-Gas Analyzer), which heats soil in an oven and analyzes
gases driven off with a mass
spectrometer, has come up empty.
"While the WCL tastes the sample, TEGA
has the ability to sniff it. You might think we'd be smart to smell something
before we tasted it, but frankly I've made the same mistake with sour milk a
number of times," joked Michael Hecht, MECA science lead with the Jet Propulsion Laboratory. Clearly elated
over MECA's discovery, more of his humor which surfaced in the teleconference
can be discovered at the end of this story.
Yesterday, NASA scientists took the unprecedented step of
making the perchlorate discovery public earlier than it traditionally would. "We're
doing this in the spirit of openness into a better understanding of how science
is done. That's the tradeoff of making this research public earlier than
planned," said Michael Meyer, chief scientist of the Mars Exploration Program.
The teleconference also attempted to quell the perchlorate rumors
that cropped up over the weekend in space blogs and news stories. One CNN report
(since updated) asserted Martian soil was toxic and suggested the planet could
not support any life.
"Finding perchlorates is neither good nor bad for life, but
it does make us reassess how we think about life on Mars," Hecht said. The half
dozen scientists on the teleconference yesterday were neutral (one was slightly
positive) as to whether the finding enhanced or hurt the prospects of finding
life on Mars.
NASA scientists continue to eliminate explanations that the
cause of their findings was something other than perchlorate. For instance,
perchlorate is used as an oxidant in rocket fuel and could have come from the
Lander, but scientists are reasonably confident it did not given the intense focus on
making sure the instruments are not contaminated.
Perchlorate, according to NASA, is a charged
particle consisting of one chlorine atom and four oxygen atoms. Wikipedia lists nine
different types and it can exist in nature or be manufactured. Perchlorate applications
are just as diverse: It can be used to treat hyperthyroid conditions or can act
as an oxidizer in rocket fuel. In nature, according to NASA, it is found in hyper-arid
climates such as the Atacama Desert
in Chile which is 50 times
drier than Death Valley.
So far, MECA and its 26 ion-detecting sensors have stolen the
perchlorate show. TEGA, according to William Boynton, science lead at the University of Arizona which co-built the device with
of Texas/Dallas, has failed to conclusively find perchlorate in two
attempts although the soil samples it used were different than the ones used by
"We found high temperature release of oxygen (in one) and
suggested this could be due to perchlorate or other possibilities that were
still open," said Boynton. However, the first test was conducted before they
were aware of the MECA's finding. After TEGA was reprogrammed to detect
chlorine which could indicate the presence of perchlorate, a second sample was
analyzed but no chlorine was found. Chlorine suggests the presence of
perchlorate, but does not have to be present for it to be found, Boynton said.
âWe have much work to do and you'll get a final story on
this sometime in the future," Boynton said, sounding much like the traditional 'it'll be ready when it's ready' scientist (perhaps not surprisingly, Hecht was
in a more talkative mood).
The workings of MECA â "a suite of instruments that include
four wet chemistry cells, thermal probe at end of robotic arm and two
microscopes" â and the drama discovering the perchlorate are best described in Hecht's
"The basic recipe is simple. We first thaw a container of
soaking solution that is mostly water and dispense it in our instrumented
beaker and wait awhile for all our sensors to recover from their long frozen
trip to Mars. We then add soil and simmer it for several hours stirring
"Throughout the measurements, we monitor the 26 sensors that
line the walls of the beaker. The majority of these sensors are ion-selected
electrodes which means they mostly respond to particular type of ion such as
sodium, magnesium, potassium, chloride or perchlorate. The 'mostly' is
important. We always need to eliminate unusual sources for the signals and that
is part of the reason it takes us so long to report on the data.
"The perchlorate was discovered with a multi-use sensor that
also has a small sensitivity to other ions such as nitrate, which is part of our
calibration solution. Let me explain what I mean by multi-use. If we had a tiny
signal from that sensor, it could mean we had a little bit of perchlorate or it
could mean we had a lot of nitrates. But a big signal from the same sensor is
almost certainly from perchlorate because even if our entire sample were made
of nitrates, it would not be enough to produce a response that large.
"When we got our first soil sample Rosy Red back on Sol 30 (a
Martian day) and saw a big signal from the perchlorate sensor, we naturally
assumed it wasn't working properly. Certainly, there could not be that much perchlorate
in the sample. A flurry of lab work in subsequent days convinced us that the
sensor was working properly and we were able to reproduce the reading with
solutions we intentional spiked with perchlorate.
"Our second WCL cell was analyzed on Sol 41. We saw a
similar response from the perchlorate sensor. We were convinced that it was a real
indication of perchlorate in the sample because we had now a) reproduced the
signal on Mars, b) reproduced it in laboratory and c) eliminated the other likely
explanations such as interfering ions.
"But we still had three more tasks to do before we were
ready to make a scientific or a public announcement. One was to eliminate some
of the more unlikely explanations because it's an unusual finding so in fact
we need to entertain unlikely explanations. A second was to increase our
understanding of the results by discussing it in detail with colleagues. A
third was to verify that the result is consistent with other Phoenix measurements and observations."
Most of those three perchlorate showstoppers have yet to be
Here's Hecht's other jokes. Hecht, of course, mentioned
the stereotype about scientists not getting dates in high school. And given he
works in California and is from Massachusetts, he opened his remarks with a
denial that the MECA team had any involvement in the Manny Ramirez trade from
the Red Sox to the Dodgers.