Mars mission success rate

The early years were a lottery

Of the 25 Mars missions launched before 1990 that have a final result, 6 fully succeeded. The first two attempts, Mars 1960A and 1960B, both failed in the third stage of the rocket and never reached Earth orbit. In 1962 the escape stage of Sputnik 22 exploded in orbit, Mars 1 lost contact on its way, and Sputnik 24 stayed in Earth orbit. In 1964 NASA's Mariner 3 failed when its shroud didn't separate and its solar panels couldn't open.

Then Mariner 4 flew past Mars on July 14, 1965. It returned 21 pictures from 9,846 kilometers away, the first full success on the list.

The launches of 1971 and 1973 show why the middle grade exists. Mariner 8 was lost when its Centaur stage lost control, and Kosmos 419's escape-stage timer was set wrongly. Mars 2 and Mars 3 each sent an orbiter that worked and a lander that didn't, and Mars 3's lander fell silent seconds after touchdown on December 2, 1971. In 1973 the Soviet Union sent four more spacecraft. Mars 4 failed to enter orbit but returned images. Mars 5 returned images before a loss of pressure ended its work. Mars 6 sent atmospheric measurements during descent before contact ended. Mars 7 missed the planet. Three of the four are graded partial, and none did everything it was built to do.

By decade

The first years were the costliest. The Soviet Union launched at most Mars windows from 1960 to 1973 and lost most of what it sent, and the United States had early failures of its own. Reliability improved as rockets, radios and spacecraft matured and as each loss was studied.

What changed

The last Mars mission lost at launch flew in 1971. Since 1996 the 8 failures were 3 stranded in Earth orbit, 2 lost on arrival and 3 lost on landing, and the most recent launched in 2011. Launch and stranding together account for 11 of all 22 failures.

By kind of mission

Orbiters have fully succeeded 44% of the time and missions that carried a lander or rover 43%. The two are close, but a failed landing usually ends a mission in minutes, with no second try.

Rates use missions with a final result, so ESCAPADE isn't graded yet. Partial counts as not a full success, so the figures are strict.

The 1990s: six losses in eight missions

The 1990s were the worst decade on the list. Only 2 of the 8 missions launched in them fully succeeded. Mars Observer lost contact in August 1993, three days before orbit insertion, as its propulsion system was being pressurized. Mars 96 failed to leave Earth orbit on November 16, 1996 and took an orbiter, two landers and two penetrators with it. Japan's Nozomi had propulsion, power and communications problems and never entered orbit.

Then came the two losses people remember. Mars Climate Orbiter was lost on September 23, 1999. The investigation found that the effect of its thruster firings had been underestimated by a factor of 4.45, because thrust data arrived in imperial units where metric ones were expected. Mars Polar Lander and the two Deep Space 2 probes were lost on December 3, 1999. NASA's review traced the probable cause of the lander's loss to the premature shutdown of the descent engines, a result of software that was vulnerable to transient signals. The probes never sent a signal, and the review found no probable cause for them.

Since 2000: a different record

The next decade looks nothing like the last. Of the 7 missions launched in the 2000s, 6 fully succeeded, and the one that didn't was Beagle 2, the British lander. It was released from Mars Express on 19 December 2003 and never called home, and a NASA orbiter found it on the surface on 16 January 2015. The same decade brought Spirit and Opportunity, each designed to last 90 Martian days. Spirit drove 7.7 kilometers before it stuck in soft soil on May 1, 2009. Opportunity covered 45.16 kilometers and was heard from for the last time on June 10, 2018. Both are on the rover list.

The 2010s were more mixed: 4 of 8 missions fully succeeded. Phobos-Grunt never fired its engine to leave Earth orbit in 2011 and took China's Yinghuo-1 with it. ExoMars 2016 and InSight are graded partial. In ExoMars 2016, the Trace Gas Orbiter did its job while the Schiaparelli lander fell freely from about 3.7 kilometers and hit the surface at an estimated 540 km/h. InSight met its seismology goals but couldn't make the deep heat-flow measurement it also needed.

Landing is the hard part

Orbiters have fully succeeded 44% of the time and missions that carried a lander or rover 43%, but the numbers hide how different the two jobs are. An orbiter that misses its insertion burn is lost. A lander faces that and a descent that has to work the first time. NASA describes Curiosity's arrival on August 6, 2012 (UTC) as seven minutes from the top of the atmosphere to the surface, and the radio delay means mission control learns the result after it has happened. You can work out that delay with the light travel time calculator.

The recent successes come with changes that answer old failures. Perseverance, which landed on February 18, 2021, used a system called Terrain-Relative Navigation. 7 of the 22 failures were lost at Mars, on arrival or on landing, and that's where much of the engineering effort has gone.

What the percentages leave out

The rates on this page are strict. A partial result counts as not a full success, so a mission that returned most of what it was built for still sits outside the success column. The rates also give every mission the same weight. The "other" group in the table holds impactors, technology demonstrations and sample returns, and a small demonstration is easier to pass than a rover. The share since 1996 rests on 26 missions: 16 full successes, 2 partial and 8 failures.

Timing plays a part too. Launch windows open about once every 26 months, so each result rests on a handful of launch dates, not on a steady stream of attempts. A rate calculated from the past can't tell you the odds for the next window. What it does show is where missions have been lost. For the full run of results, see every Mars mission.

First tries, and the ones that didn't work

Recent newcomers did better than older averages suggest. India's Mars Orbiter Mission entered orbit on September 24, 2014 in its first attempt, at a cost ISRO gives as about 450 crore rupees, about 80 million US dollars. The United Arab Emirates' Hope orbiter arrived on February 9, 2021, making the UAE the first Arab country and the fifth country overall to reach Mars. China's Tianwen-1 delivered an orbiter and, with Zhurong, a rover in one mission. But a first try is no guarantee: Nozomi and Phobos-Grunt are on the failures list, and the programs are compared on countries that have reached Mars. The planet all of them were aiming for has its own page, Mars.