[FPSPACE] Russian Mars 2, 3 landing sites [Our Ref:EXA14538]

[Geert Sassen]

Mars 3 and 6 are just one of those mysteries which keep popping up.

For Mars 6 there is a very interesting presentation made by Viktor Kerzhanovich (JPL) and Konstantin Pichkhadze (Lavochin) in Lisbon on 6-9 oct. 2003 during a workshop on planetary EDL, if you like I can send you a copy of it. This gives quite a lot of amazing details on admospheric science results both from the Venera venus landers as well as  from the Mars 6 descent.

On of the graphs shows the (doppler derived) descent speed of Mars 6 with very clearly a sharp drop in speed at the moment the parachute was deployed, so this certainly worked. However, afterwards the speed slowly starts rising again which might indicate that the parachute either ruptured or collapsed  (read many other papers on the difficulties of designing parachutes for the Marsian EDL conditions). On the other hand, there are many conditions which might have caused a slow rise in descent speed. The final descent speed can not be accurately read from the graphs, but a figure of 63 m/sec has been mentioned in the past, this is 'fast' but not absolutely 'deadly'. The soft landing rocket was designed to correctly slow down the craft from a initial speed of up to 60 m/sec, so if this engine fired the craft might still have survived its landing, although it definitely landed very hard.
At the moment the soft landing rocket fired, the radio equipment was switched off conform plan, and all communications terminated, so the fact that contact was lost does not in itself indicated that the thing crashed.

According the earlier mentioned booklet by V.G. Perminov Mars 6 carried two completely independent transmitters, working on different frequencies. One set was mounted on the parachute frame and transmitted admospheric EDL data to the Mars 6 mothership, and this is the data which is available. The other transmitters were installed in the landing craft (identical to Mars 3) and seemingly could only transmit via a relay by the Mars 5 orbiter. If this is true (and I see no reason to doubt Perminov) and the Mars 6 mothership did not have relay equipment for surface-transmissions, then the 'silence' from the Mars 6 lander is easily explained for the Mars 5 orbiter was long dead by the time Mars 6 landed, so without an orbiting relay post contact was simply impossible. Even before the landing attempt the Soviets must have known that there was no way to ever receive information from the Mars 6-7 landers after touch down...

With regards to Mars 3 I never found any mention of any transmitter on the landing frame, and Perminov seems to imply that this transmitter was only mounted on the Mars 6/7 landers and not on Mars 2/3. So it sounds like Mars 2 and 3 descended in silence (just like MPL and the Beagle landers...) and only started transmissions after landing. We know that Mars 2 was released in the wrong orientation and entered the admosphere at a very steep angle, causing it to crash on the surface before it ever had a chance to deploy its parachute. Finding wreckage of that craft is seeking for a needle in a haystack. Mars 3 clearly survived its landing and several minutes after landing (when all antenna were deployed) it started transmission of the first images, however after 14.5 seconds all signals abruptly stopped and the craft was never heard of again. Personally I have the strong suspicion that this failure was caused by the relay equipment in the Mars 3 mothership and had nothing to do with the lander. Those landers were in many aspects identical to the Luna 9-13 landers and the Venera landers and all of those craft proved to be very sturdy so this was not 'untested' equipment and there does not seem to be reason to assume the Mars 3 lander was less perfect then its Lunar and Venusian counterparts. On the other hand, we know for certain that the Mars 3 mothership had big problems at about the same time it was receiving the signal from the lander. It lost 3d stabilisation, started tumbling, and cut short its orbit insertion burn, ending up in an extremely eccentric orbit with a period of almost 2 weeks instead of the intended 25 hr orbit. Only after several attempts did groundcontrol succeed in re-establishing radio contact and proper orientation of the mothership. If the craft was tumbling while it was receiving the signals of the lander, it is reasonable to assume it might have lost lock on the signal and this would indeed cause an abrupt end to the signal relay. Certainly the lander never got a second chance: it was intended to automatically stop transmissions after aprox 20 minutes and resume transmissions the next day when the mothership passed within radio range again, but with the mothership in the completely wrong orbit it took at least two weeks before there was ever a second relay-option, and by that time the lander batteries were long exhausted...

Regarding the search for the Mars 3 lander, I guess there is almost zero chance of finding it. Even on the best HiRISE images it will be very hard to see the difference between a 'normal' rock and this lander and its parachute will probably have been covered by dust long ago (even the Viking 1 and 2 parachutes are difficult to see). Most of all, landing coordinates are extremely uncertain. Remember this was before even the Mariner 9 orbiter completed its mapping mission, so accurate charts and data of Mars were not available. Furthermore there are many different coordinate systems for Mars and the coordinates mentioned for Mars 3 might not be the same as the coordinate system used nowadays with the HiRISE images (errors of many hundreds of miles or more might be caused by this). I think this explains why nobody has yet searched for it. For Mars 6 there is a little more data to go by and its coordinates MIGHT be slightly better, but still chances of finding it are almost zero I expect.

In the "search for old spacecraft" I guess the big price will be the location of the Luna 9 lander on the moon, there will be a search for it using the LRO images once available and given the nature of the moons surface it might very well be possible to actually find the thing. Good hunting!