Sunday, July 17, 2016

Viking Vibes and Mars Memories: Viking Forty Years Later, Part Three

NASA image: "Mariner 4 image, the first close-up image ever taken of Mars. This shows an area about 330 km across by 1200 km from limb to bottom of frame, centered at 37 N, 187 W. The area is near the boundary of Elysium Planitia to the west and Arcadia Planitia to the east. The hazy area barely visible above the limb on the left side of the image may be clouds. This portion of the feature has been enhanced in image m04_01h to bring out more of the haze-like features. The resolution of this image is roughly 5 km and north is up. (Mariner 4, frame 01D)"
More Space Myths Busted: There Were Mars Missions Years Before Viking

I was reading an online article recently (source redacted) that characterized the Vikings as the first robotic missions to visit Mars. While the Vikings made the first successful landings (read: returning useful data) upon the Red Planet, they were far from the first spacecraft to explore our planetary neighbor.

Several efforts to investigate Mars had been made by both the United States and the Soviet Union well over a decade before Viking 1 sent back its first image (of its foot!) on July 20th, 1976. This blog post seeks to survey these missions, and their results (successful, or not). 

The Soviet Union’s Pre-Viking Mars Missions

The USSR’s attempts to explore Mars through flybys began as early as 1960, according to RussianSpaceWeb.com. After three missions felled by third- and fourth-stage rocket failures, the USSR successfully launched Mars 1 on November 1st, 1962. However, contact with the spacecraft was lost on its way to Mars at 105,000,000 km (approximately 65 million miles). So close, but yet, still so far away. Zond 2 was launched on November 30th, 1964, but suffered a similar fate. Two 1969 missions failed during launch, and a 1971 mission designated Kosmos-419 didn’t make it past Earth’s orbit.

Two 1971 missions showed more success. Mars 2, launched on May 19th, 1971, managed to orbit Mars, and deployed a capsule to its surface. While the capsule did not descend as intended, it did become the first man-made object to impact itself upon the Red Planet. Mars 3, also launched in May 1971, too orbited the Red Planet, snapping several pictures.

Its lander (which even possessed a small rover!) managed to touch down upon Mars’ surface five years prior to Viking 1 settling down upon Chryse Planitia. However, the lander stopped transmitting data back to Earth within 20 seconds. It has been theorized that this failure may have been the result of damage caused by a severe dust storm taking place on Mars at the time.

Further attempts at Mars shots followed during 1973. Mars 4 and Mars 5 were both launched in July 1973; Mars 4 just missed the planet by 2,080 km (approximately 1,300 miles) after the failure of onboard computers, and Mars 5 failed after nine days in Mars’ orbit. Mars 6 and Mars 7 were both launched in August 1973. Mars 6’s flyby bus released a lander; however, contact was lost within minutes of it entering its landing sequence. Mars 7’s lander would miss the planet by approximately 1,280 km (800 miles).

Putting The USSR’s Mars Missions In Context

It would be easy for some to be critical of the USSR’s Mars shots, as they yielded many failures. However, here are a few things to keep in mind:
  • The USSR successfully landed several Venera spacecraft upon Venus’ surface between 1970 and 1981. This was no easy feat, given the hellishly high temperatures and pressures on that planet. The Soviets, as far as I am aware, possessed the only images of Venus’ surface as seen from a lander. The USSR also sent cloud balloons to Venus, which is almost too cool to comprehend.  
  • Landing on Mars is arduous. Keep in mind that the USSR’s landing attempts were made well before extensive surveys of the planet had been done. Landers can be rendered useless if they land within a crater, on a rock, or in an uncomplimentary area. Several landing sites for both Vikings had been rejected for being potentially too dangerous.
Also, the atmosphere presents challenges. The January 1977 National Geographic puts it best: “The landing process itself would be technically complicated. Descending through the Martian atmosphere is much trickier than landing on the airless moon.” If anything, the United States probably learned a great deal about landing on Mars, even in a limited way, from the Soviets’ attempts.

(To also be fair, the U.S. has also had its share of Mars mission failures; some of these occurred years after both Viking landers rested in peace at their respective landing sites, but that’s a story for another time.)

The United States’ Pre-Viking Mars Missions

The United States’ Mars odyssey also began in failure on November 5th, 1964 with Mariner 3, when the payload fairing on its Atlas-Agena launch vehicle didn’t separate as planned. The spacecraft, starved of power, died within hours of its launch. 

The disappointment from that attempt would be replaced with pure joy within the next year. Mariner 4, launched on November 28th, 1964, would return the first images ever of a planet from the recesses of deep space during its July 1965 flyby. While its 21 pictures seem downright rudimentary by today’s standards, this mission advanced the deep space race by leaps and bounds at the time. 1969’s Mariners 6 and 7 would return 75 and 126 pictures respectively during their flybys, while also analyzing the Martian atmosphere.

As you may have gathered earlier, spacecraft are at the mercy of their launch vehicles during the earliest stages of their missions, and Mariner 8 was no exception. Its May 1971 launch saw it “explore” the depths of the Atlantic Ocean following a failure of its Atlas-Centaur launch vehicle (one small problem: it was supposed to go to Mars).

From NASA: "Mariner 9 image of the north polar cap of Mars. The image was taken on 12 October 1972, about one-half Martian month after summer solstice, at which time the cap had reached its minimal extent. The cap is about 1000 km across. The interior dark markings are frost-free sun-facing slopes. A smooth layered sedimentary deposit underlies the cap. The image is centered at 89 N, 200 W. (Mariner 9, MTVS 4297-47)"
Mariner 9, also launched in May that year, was destined for a much happier fate, becoming the first spacecraft to orbit Mars (or any planet outside of Earth, for that matter) in November 1971. It returned 7,329 images before it was decommissioned on October 27th, 1972. The next stops for the USA were Vikings 1 and 2, respectively launched in August and September 1975. And as they say, the rest is history.


Remember The Vikings

Viking 1’s lander remained operational as kind of a Martian weather station until November 11th, 1982; its sister at Utopia Planitia, Viking 2, breathed its last on April 11th, 1980 due to a battery failure. The images from both landers are now largely superseded by those from, say, the Mars Curiosity rover, which has provided 360-degree, high-resolution panoramas of Gale Crater since mid-2012 (it even has returned “selfies”).

While the Vikings couldn’t rove, and didn’t have the imaging capabilities of later landers and rovers, they will forever possess the honor of first showing humankind the surface of our friendly red neighbor, and continue to inspire spirited discussion of whether life truly does exist on other worlds.  
From NASA: "Viking 2 Lander image showing the spacecraft and part of Utopia Planitia, looking due south. Note the American flags, color grid, and bicentennial symbols on the spacecraft, which were used for color balance. The RTG (radiothermal generator) cover is in the foreground with the flag. The S-band high-gain antenna is at the top center, and the other RTG cover is at the left. The image spans an azimuth of about 140 degrees. The image was taken at 12:20 lander local time. (Viking 2 Lander, 21C056)" 
For information about Viking at 40 events occurring during the upcoming week, check out this link. Many thanks to Jay Gallentine for his input.

Sources/Recommended Reading:

1. Gallentine, J. (2015). Infinity Beckoned: Adventuring Through the Inner Solar System, 1969-1989. Lincoln, NE: University of Nebraska Press.
2. Gore, R. (1977, January). Sifting for Life in the Sands of Mars. National Geographic, 151(1), 3-31.
3. Moore, P., & Hunt., G. (1983). Atlas of the Solar System. Chicago, IL: Rand McNally & Company.
4. Mutch, T. (1978). The Martian Landscape. Washington, D.C.: NASA Scientific and Technical Information Office.
5. Zak, A. (2016, June). Russia’s Unmanned Missions to Mars. In RussianSpaceWeb.com. Retrieved from http://www.russianspaceweb.com/spacecraft_planetary_mars.html