

By Lisa Rein















Photo: NASA / JPL / Malin Space Science Systems

MB: Yes.

LR: So, how’s it going? Is the Tryptophan reacting?

MB: No. It’s not going well yet, frankly. It’s hard. I keep trying things, and things keep not working. What’s important to understand is that this is normal. “Failure is the inventor’s constant companion.” (One of the few things that Thomas Edison said that we don’t think he ripped off of anyone else.)

For example, if you go to the hardware store and buy a bottle of WD-40. WD-40 stands for “Water Displacement,” because it’s not a lubricant, it’s a water displacer. The “40” comes from the “40th attempt” at making it correctly. Now, just imagine how rusty everything would be if they had given up on number 39? This is Research and Development. If it was easy, someone would have done it already.

LR: So far, the problems you’ve encountered were either with the laser having no effect or burning it up completely? (Including burning a hole in your living room curtain.)

MB: Exactly. Figuring out how to get the Triptophan to react to the laser hasn’t really come easily. I really got lucky last time when I happened upon the Chlorophyll reactivity to the lasers I was working with. Then I had to do my homework in order to capitalize on that luck.

It happened one day when I was making my lasers and playing around with infrared vision. I noticed that when I went outside and put an infrared filter on the phone to take pictures — that if you filter out just the right wave lengths, you can tell whether something is green because it’s a plant, or whether something is green because it’s painted green. That was interesting. I then figured out that, by coupling that with sending the laser at just the right laser frequency (so the Chlorophyll would fluoresce a little bit), I was able to detect whether a sample of anything contains Chlorophyll or not.

The interesting thing is that, if you looked this up in a textbook, you would find that the Chlorophyll actually fluoresces at a completely different frequency.

LR: So, what were you doing differently with the laser?

MB: I was sending sufficient laser light to the Chlorophyll so, instead of catching its florescent frequency, I caught one of its harmonics.

Now, this is something that normally radio waves do, and you know, a photon and a radio wave are the same thing; they are both still made up of photons. So all I had to do was look a little further.

LR: Explain what you mean actually by “catching its harmonic.”

MB: Some substances will fluoresce by emitting a light frequency when they receive another. Since there is “no free lunch” (meaning everything requires some energy), the frequency emitted is always at a lower wavelength than the original. This is in theory. In practice, there will be emissions at even lower frequencies as well, albeit weak ones. This one just happened to be, barely, in the range where a regular camera can pick it up, with the appropriate filter installed.

My method is very energy inefficient, but who cares. I’m only “wasting” about a watt of power, so, it’s an acceptable loss. However, it lets me find Chlorophyll without having to cut up a sample – which would require an articulated arm that would probably use more power than the laser anyway, and have the disadvantage of being complicated and easy to break. So this way, I can just scan for a molecule, as the rover moves around, it can have a downward facing sensor that will say “hey! there’s something here.”

LR: Time to stop and dig!

MB: Yep. For Tryptophan, we are trying to do the same thing that we did with the Chlorophyll detector. The problem is that Tryptophan is a somewhat more compact molecule.

LR: Okay. “More compact.” What does that really mean?

MB: It means that, for its resonant frequencies, instead of being in the infrared, they are all in the ultraviolet. This causes two problems. 1) If I have to give it a higher frequency, I have to go into the deep ultraviolet, which frankly, is expensive; the parts for it are expensive. And 2) For chlorophyll, the excitation laser is visible. It’s a deep purple. (That means I know where it’s safe to look at the reflection or not.) So, that’s why the process went much faster. I could see the laser I was tuning, and I didn’t have to worry about an invisible laser burning my eyes.

Left, Old Laser Part. Right, New Laser part for creating a laser in the “Deep Ultraviolet” region.

LR: You mentioned that you have already purchased some of those expensive parts required for going into the deep ultraviolet. How did they work so far?

MB: Yes I bought 10 of them, at $90 each, and I have already blown out two of them.

LR: How are you “blowing them out” exactly?

MB: Too much current. I haven’t yet figured out the thermal curve for them, so they just avalanche.

LR: “Avalanche?” What does that mean?

MB: Well, with most analog things, when you heat them up, they actually resist current more. But diodes are an exception; when heated, they resist current less. So what happens is, you start running your diode. It heats up. It absorbs more current, which causes it to heat up even more, and in about 1/100th of a second, the thing “avalanches” and cooks itself.

LR: It just fries up, or melts, or what?

MB: Well, it’s only a microscopic part of it that actually melts; but that doesn’t matter. It’s not working anymore.

LR: What are you doing wrong? How are you overloading it? And I have a feeling I won’t understand the answer, but for folks that might…

MB: I need to couple it with a component that has the thermal coefficient of greater magnitude in the opposite direction

For the Chlorophyll-detecting lasers that I already have, I have figured out the right part: it’s actually this old voltage regulator from Texas Instruments that can be adapted to this purpose. But as for the new stuff; I haven’t figured that out yet!

LR: So, you were saying how, for the Tryptophan laser, it’s a type of laser that will cause a reaction cannot be visible, and that it is a safety problem. Why?

MB: Because if I can’t see the laser, should I look at it when it’s on, I won’t “see” it go into my eye until it’s already caused damage to it. So I have this potentially eyeball-destroying laser, since my eye cannot see if it’s on or not.

To address this — because, ya know, I’ve got two eyes and I’d like to keep both of them — it means I have to have a reasonable amount of safety mechanisms. A reasonable amount meaning “at least two.” These are: safety glasses I’m wearing and the use of a box to contain the laser and material I’m working with. Even with the safety glasses on, I can’t see the laser, so I still need to have the experiment completely contained, as even the reflection of this laser could be blinding.

You can see how this decreases the number of tests that I can run in a single day. Since I have to put the tryptophan in the box, hit it with the laser, and then take it out of the box to see the effect it had. That means that the work is naturally slower, because every time that you try to change something, you have to take it out of the box, do your thing, put it back in the box, and turn the interlock back on.

LR: Wow. You have to do all that just to be safe?

MB: Yes. Much like the Chlorophyll detector, it requires some amount of fine tuning. But unlike the chlorophyll detector, I can’t peek at the reflection.

With the Chlorophyll detector, I could see the light with my eyes, without hurting them, so it was easy to know if the laser was turned on or not. But, with the Tryptophan detector, it’s all in the deep ultraviolet, so I cannot see what I am doing without endangering my eyes. So I have to keep everything in the box and adjust it a little bit. And check. Then adjust it a little bit more. Check. Like that. So it’s a much longer process.

LR: Well it’s important to do it safely. But hey, that still seems like progress. Why did you sound so discouraged earlier?

MB: I’m not discouraged, but I am hoping for a flash of inspiration that has not come yet. I am making the assumption that the method I came up with for detecting Chlorophyll might apply to Tryptophan. But maybe it just doesn’t. Maybe I’m barking completely up the wrong tree. I don’t know yet. An issue is that… according to current theory, my Chlorophyll detector shouldn’t work, and since it does, that means the math needs an update. I think Heather (NASA’s Heather Smith) is writing a paper about how my system works, and I look forward to reading it so I can know what I did right!

If you try to fluoresce something, in addition to fluorescing it, the frequency that it fluoresces at, it will actually fluoresce a little bit on some harmonics, which are easier to detect.

LR: But you said it didn’t fluoresce. You said it was in the ultraviolet region?

MB: Yes. It (Tryptophan) fluoresces in the ultraviolet region. Fluorescence isn’t just “glow in the dark” stuff or blacklight stuff. That’s just the “fluorescence” we can see.

LR: (Lisa looks up “fluorescence” on Wikipedia, which tells her: “Fluorescence is the emission of light by a substance that has) absorbed light or other electromagnetic radiation. It is a form of luminescence.”

Ok. So we are trying to get the Tryptophan to absorb light. Got it!

MB: Yes. It means that you’re feeding it photons and it’s spitting some of those photons back at you at a lower frequency, hence the fluorescent glow.

LR: Ok cool. So! So far, you’ve been hitting it with ultraviolet laser beams in this controlled environment. And what has the reaction been?

MB: The reaction so far has been nothing. So, I upped the power a little bit. Nothing. I upped the power a little bit, and repeated that about 20 times. And then I’m just shooting it with too many photons, and it just catches on fire.

LR: So you’re looking for that sweet spot between nothing and catching it on fire?

MB: Yep.

LR: Is there anything about the frequencies being ultraviolet that give it different properties that need to be taken into account while you’re dealing with the latter (Tryptophan).

MB: There is. For one, they are ionizing radiation. So they are potentially cancer-causing. Another reason to be careful.

LR: Oh. Hmmm. I think I’ll leave before you resume these experiments. 🙂

MB: It’s part of why I don’t really have a demo to show you yet. I have to be very very careful. As I was explaining earlier, although I cannot see them, the energy is enough to destroy your eyes. And regular goggles don’t protect you against these ultraviolet rays. In addition, it’s not the same ultraviolet you get from the sun. This is higher frequency stuff, half way to X-rays, and there are no glasses that filter it completely. (Although I do have some I wear that provide some minimal protection, in addition to keeping the entire experiment “in the box.”) But that’s okay. I’d rather work slowly and safely.

It’s less interesting to look at because all I am doing is putting stuff in a box and reading a result. Now, all of this safety stuff is not going to be an issue on Mars because there’s nobody there. So, this thing will be able to hang out in the free air – or what little air there is on Mars.

LR: Well wait a minute, might there be other life on Mars that you don’t want to expose with these ultraviolet rays? Are you saying there’s so many ultraviolet rays coming from the sun already that it won’t matter? I thought you said these were different than the sun’s ultraviolet rays?

MB: No. I’m not saying that. I’m saying that we’re looking for small traces of something alive. If we happen to hit an actual animal with this laser, and it runs away, well, that settles the question, no? Realistically, we’re looking for microbes at the moment.

LR: I know but just because we might have that questions answers the “life” question, doesn’t mean we want to just fry whatever it is with ultraviolet rays, right?

MB: Yes. That’s an important issue. I certainly don’t want to be the one that finds life on Mars and then kills it instantly.

LR: So it is a consideration. It should still be kept in a box, when it’s used on Mars. No matter where it is.

MB: Well, not in this case, as that would defeat the point of the design. The point of this thing is that it will be able to shoot two different kinds of lasers right out from the bottom of rover, with one type of laser looking for Chlorophyll, and another type of laser looking for Tryptophan.

The whole point is for the next Mars Rover to be shooting these lasers out from its bottom as it moves along the surface of Mars. So, no, there’s no box to be opened and shut, as the whole point is to be searching for these substances in real time, as it is moving along.

LR: Okay. But I don’t like it. I mean, what about other forms of life on Mars that we just don’t know how to find yet? The laser could affect them?

MB: Well, for that consideration, you need to talk to the Planetary Protection Officer at NASA. Is that the coolest job title or what? Incidentally, there was an interesting debate between John Rummel (former NASA Planetary Officer and current Senior Scientist with the SETI Institute) and Robert Zubrin (President and Founder of the Mars Society) about what’s an acceptable risk. (See: “What Are We Protecting Mars From — And Why Do We Bother?”)

LR: It’s an important consideration that people aren’t taking very seriously with regard to Mars lately, in my opinion. Despite the fact that we keep finding evidence that there could be life there.

Coming soon: Matteo explains the significance of last month’s Methane discoveries on Mars.

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