On Sept. 15, 1968, the Soviet Union launched the Zond 5 spacecraft on a mission to loop around the moon and return to Earth. There were no cosmonauts aboard, but there were several smaller vertebrates — including the first two tortoises to ever go to space!

Other passengers included wine flies, mealworms, plants and seeds. These were the first animals in deep space and the first to travel around the moon.

• Photos: Pioneering Animals in Space

After looping around the moon, the Zond 5 spacecraft turned around and came back to Earth. It was supposed to land in Kazakhstan on Sept. 22, but the spacecraft's guidance system failed, and it splashed down in the Indian Ocean instead.

The Soviets did recover the capsule and found that the tortoises and other critters were still alive, although they had lost some weight since the start of the mission.

Why it mattered

In September of 1968, the Space Race to the moon was in full swing. NASA was just three months away from the historic Apollo 8 mission, which sent the first astronauts around the moon in daring first-of-its-kind mission.

But with Zond 5, the Soviet Union scored an early win for the first circumlunar flight that launched from the Earth to the moon, then returned for a landing (or splashdown, in this case). In fact, the flight may have spurred NASA to launch Apollo 8.

"The flight of Zond 5 caused concern in the U.S. that the Soviets would place cosmonauts aboard the next Zond and complete the first crewed circumlunar mission. At about this time, a U.S. Corona reconnaissance satellite photographed an N-1 rocket on its pad at Baikonur," NASA wrote in a report, adding that NASA's then-chief James Webb likely saw those intelligence reports.

"The apparently successful Zond 5 mission coupled with the photos of the Soviet lunar booster on the launch pad may have contributed to the decision to send Apollo 8 on its circumlunar mission in December 1968, bringing the moon landing one step closer."

Zond 5 launched from Baikonur Cosmodrome atop a Proton rocket and took three days to reach the moon. The two tortoises on board were, appropriately, Russian steppes tortoises, NASA has said. After looping around the moon, the critters spent a few more days in transit for the trip home.

It was a guidance system error that led the Zond 5 capsule to splash down in the Indian Ocean instead of landing on land as planned. But the landing on Sept. 21 wasn't the end of the road for the Zond 5 tortoises and other animals.

The Soviet recovery ship Vasily Golovnin plucked the Zond 5 capsule from the ocean and returned to port in what is now Mumbai, India on Oct. 3, weeks later! They wer ethen flown to Moscow on an Antonov-12 cargo plane before the capsule was finally opened to find the tortoises alive and in good health. You can still view the Zond 5 capsule at the RSC Energia museum in Korolev.

Cassini's Grand Finale death dive at Saturn in 2017

A bunch of space traveling tortoises and other animals aren't the only notable space event that happened today in history.

On Sept. 15, 2017, NASA's Cassini spacecraft died in a blaze of glory as it crashed into Saturn after 13 years orbiting the ringed planet. NASA ended the mission in a fiery plunge because Cassini was running out of fuel and the space agency wanted to ensure it wouldn't crash into one of Saturn's icy moons, like Enceladus, and contaminate them. They called it Cassini's Grand Finale.

Launched in 1997, the $3.26 billion Cassini mission entered orbit around Saturn in 2004 and dropped a European Huygens probe onto the cloudy moon Titan in early 2005. The mission was expected to last until 2008, but was extended twice, ultimately stretching through to September 2017.

During its mission life, Cassini discovered a trove if new Saturn moons, found a strange hexagon at the planet's north pole and tracked mesmerizing details of the planet's many rings.

"Congratulations to you all," Earl Maize, the Cassini program manager, said to the mission team after the spacecraft signal was lost."This has been an incredible mission, an incredible spacecraft, and you're all an incredible team. I'm going to call this the end of mission."

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On Sept. 14, 1966, NASA's Gemini 11 mission set an spaceflight altitude record that lasted for nearly six decades when two astronauts reached an orbit of 850 miles above the Earth. It remained the highest altitude ever achieved by a crewed, non-lunar mission until 2024.

Gemini 11 command pilot Pete Conrad and pilot Dick Gordon spent three days orbiting the Earth in their cramped Gemini spacecraft. After launch, they performed the first-ever direct-ascent rendezvous with an Agena target vehicle.

Once the two spacecraft were adjoined, they used the rocket on the Agena target vehicle to ascend to their record-breaking altitude. They also created a little bit of artificial gravity while in orbit by using their thrusters to rotate the combined spacecraft.

Why it mattered

Despite its name, Gemini 11 (or Gemini XI) was actually NASA's ninth crewed mission of the two-person Gemini spaceflights. The mission was relatively short, just three days, and included two spacewalks, and what NASA calls the first orbital rendezvous and docking with an Agena target vehicle (the first in-space docking occurred three missions earlier on Gemini 8).

But for 58 years, the Gemini 11 mission marked the highest astronauts flew above Earth without going to the moon. The astronauts used the rocket engine on the Agena booster to raise the orbit of their docked spacecraft to reach a peak altitude of 853.8 miles (1,374.1 kilometers).

Conrad and Gordon performed eight different science experiments, but perhaps one of their most striking feats was the artificial gravity demonstration. During one of his spacewalks, Gordon attached a 30-meter tether from the Agena booster to the Gemini capsule. After reaching their peak altitude, Conrad undocked the capsule from the Agena, backing away them starting a rotation that created a very slight "gravitational acceleration," NASA said. They spun together for 3 hours, before the tether was cut loose and Gemini 11 left the Agena behind.

Conrad and Gordon also performed the first automated reentry during their landing, with their Gemini 11 capsule flying itself in a first-ever for NASA.

The Earth orbit altitude record set by NASA's Gemini 11 mission stood until Sept. 10, 2024, when the private SpaceX mission Polaris Dawn, bankrolled by American billionaire Jared Isaacman (currently serving as NASA administrator), launched into an orbit that reached 870 miles (1,400.7 kilometers).

That Polaris Dawn mission also included a spacewalk by Isaacman and SpaceX's Anna Menon, marking the first-ever private spacewalk.

On Sept. 13, 2007, Japan launched the Kaguya spacecraft on a mission to the moon. Formally known as SELENE, which is short for SELenological and ENgineering Explorer, it was Japan's second moon mission.

Kaguya launched from Tanegashima Space Center on a Japanese H-IIA rocket and looped around the Earth twice before heading to the moon. NOTE: While the launch occurred on Sept. 13 in the evening Eastern Time, it was actually 10:31 a.m. on Sept. 14 at the launch site. The spacecraft carried 14 science instruments and two tiny microsatellites to map the moon's surface and study its gravitational field.

After a 20-day journey, Kaguya arrived at the moon. The mission consisted of three spacecraft: a main orbiter, a small communications satellite, and a third small satellite to map the moon's gravitational field. After about a year of lunar observations, the mission ended with a planned crash landing on the lunar surface.

Why it mattered

The Kaguya moon mission was actually the second lunar probe launched by Japan, but it was the country's first spacecraft to actually orbit the moon. (Japan's Hiten spacecraft launched in 1990, but it flew in a highly elliptical orbit around Earth that allowed it to make 10 flybys of the moon before crashing into the lunar surface in 1993. It also released a small probe called Hagoromo near the moon.)

But while the Hiten and Hagoromo missions were designed to test technology for a future moon mission, Kaguya put all that tech into practice. The probe was renamed after the moon princess Kaguya-hime from a Japanese folktale shortly after launch as a result of a public poll. The two small satellites it carried were named Okina (a relay satellite) and Ouna (a radio source experiment).

While Kaguya carried an intricate set of science instruments, it was the views from its two primary high-definition cameras that wowed the public. With them, Kaguya captured the first-ever HD video and images of the moon, including spectacular new videos of Earthrise (the Earth rising over the moon) - something not seen since NASA's Apollo missions.

The spacecraft also created an complete topographical map of the moon, detected gravity anomalies on the near and far side of the moon and captured the first optical observations of the permanently shadowed interior of Shackleton Crater near the moon's south pole, according to a NASA review.

Kaguya completed its primary mission in October 2008 and JAXA mission planners had hoped to extend its moon flight through early 2009, but a faulty reaction wheel forced them to call off the extended mission early. They ultimately directed Kaguya to crash into the moon on Feb. 12, 2009, with the impact occurring near Gill Crater.

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On Sept. 12, 1992, NASA astronaut Mae Jemison became the first African American woman to go to space.

In NASA's early days, women and people of color were never selected to go to space. NASA didn't send a woman to space until the seventh space shuttle mission in 1983. NASA launched the first Black man in space, astronaut Guion Bluford, on the following mission that same year.

• Women in Space: A Gallery of Firsts

But it would take another nine years for NASA to finally select a Black woman to fly on STS-47, the 50th space shuttle mission. Jemison was a trained engineer and licensed physician who served in the Peace Corps before applying to become an astronaut.

She worked as a mission specialist on STS-47 and logged over 190 hours in space. STS-47 was her only mission. In 1993, she retired from NASA and went on to found her own company, the Jemison Group, which is a technology consulting firm.

Why it mattered

Mae Jemison's historic launch on STS-47 was a milestone for Black astronauts and NASA's growth into a more diverse space agency.

Jemison, who was born in Alabama and grew up in Chicago, joined NASA's astronaut corps in 1987 as an astronaut candidate after years working as a the Area Peace Corp Medical Officer for Sierra Leone and Liberia in West Africa (from 1983 to 1985). Before that, she earned a bachelor's degree in chemical engineering from Stanford University (where she also studied African American Studies), and later a doctorate in medicine from Cornell University. She was serving as a General Practitioner in medicine when she applied to be a NASA astronaut.

Jemison has said she was fascinated by space from a young age and found inspiration the Star Trek's Lt. Uhura, a Black woman in space on television, before going on to university. (We'll return to Star Trek in a minute).

As the science mission specialist on STS-47, Jemison oversaw 44 different experiments for Japan and the United States inside the Spacelab module aboard space shuttle Endeavour. She was also the co-investigator on a bone cell study that flew on the same mission.

Jemison spent eight days in orbit on STS-47, logging 190 hours, 30 minutes and 23 seconds in space, before returning to Earth on Sept. 20, 1992. It would be her only spaceflight.

Jemison retired from NASA in 1993 and founding her Jemison Group. as a consulting firm that same year. Remember Jemison's Star Trek inspiration? It came full circle in 1993 when Jemison appeared as a lieutenant on "Star Trek: The Next Generation" in the episode "Second Chances" during the sixth season.

Jemison has also led the 100-Year Starship project to encourage the development of a mission visit another star. In 2017, Jemison became an official Lego minifigure in the Women of NASA Lego set.

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On Sept. 11, 1985, the International Cometary Explorer, or "ICE," became the first spacecraft to fly by a comet.

Originally launched as the International Sun-Earth Explorer-3 in 1978, ICE was one of three spacecraft built for the International Sun-Earth Explorer (ISEE) program, a joint effort by NASA, the European Space Research Organization and the European Space Agency.

The program's purpose was to study space weather, or the interaction between the Earth's magnetic field and the solar wind. After completing its original mission, the spacecraft did a maneuver to steer it toward Comet Giacobini-Zinner. It flew straight through the comet's plasma tail, but it didn't stop there! Six months later, it flew by Halley's Comet, too.

Why it mattered

The International Cometary Explorer has gone down in history as a mission of epic firsts, many of which occured after it completed its primary mission.

As mentioned above, NASA, ESA and the European Space Research Organisation teamed up to build and launch the probe in 1978, when it was called the International Sun-Earth Explorer 3, or ISEE-3. The mission was the third of three to study the sun-Earth environment, with ISEE-3 aimed at studying energetic particles, electric and magnetic fields and the plasma environment. It carried 14 different instruments, including a solar wind detector and gear to measure cosmic rays, X-rays and gamma rays.

For its primary mission, ISEE-3 flew to the L1 Lagrange point about 1 million miles (1.5 million kilometers) from Earth on the sun-facing side and spent three years conducting science. It was the first spacecraft ever to orbit a Lagrange (or libration) point, NASA has said.

But it was in 1981, once ISEE-3's core mission was over, that things got interesting for comet fans. NASA scientists at Goddard Space Flight Center in Maryland decided to squeeze more science from the probe by sending it through Earth's magnetic tail (another first), and then on to visit a comet.

That began in 1982, with the probe firing its thrusters and performing five flybys of the moon to set course for Comet 21P/Giacobini-Zinner. It was only then, once ISEE-3 was on course for the comet, that it was renamed the International Cometary Explorer, or ICE.

On Sept. 11, 1985, the spacecraft flew within 4,885 miles (7,862 km) of Comet 21P, confirming many theories about comets (including that they are dirty "snowballs" of the solar system) and collected detailed data about its tail. It also took a long-distance look at Halley's Comet on March 28, 1986, when it passed by at a range of 25 million miles (just over 40 million km).

While NASA shut down the ICE/ISEE-3 mission in 1995, it saw renewed interest in 2014 when a group of independent scientists attempted to reactivate the probe when its orbit brought it near Earth in August 2014. At the time, the probe still had five operational instruments and an active transmitter that allowed NASA to track it across the solar system. The group raised $125,000 in crowdfunding to support their effort.

The science group managed to successfully fire ICE/ISEE-3's thrusters on July 2, 2014, but subsequent efforts failed and it flew past the moon and continued on its long orbit around the sun. It should return near Earth sometime in 2031, NASA has said.

A tragic day seen from space

Another major event occurred in space history on Sept. 11, this time in 2001.

On that day, NASA astronaut Frank Culbertson was the only American in space to see the tragic 9/11 terrorist attacks on New York City, Washington, D.C. and Pennsylvania as part of a three-man crew on the International Space Station.

Culbertson was commander of Expedition 3 to the ISS and led a crew that included Russian cosmonauts Vladimir Dezhurov and Mikhail Turin.

"I didn't know exactly what was happening, but I knew it was really bad because there was a big cloud of debris covering Manhattan," Culbertson said in a NASA video released in 2011. "That's when it really became painful, because it was like seeing a wound in the side of your country, of your family, your friends."

You can learn more about Culberton's observations of the 9/11 attacks from space at NASA's Remembering 9/11 site here.

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