O'er the fields we go… Not long before their splashdown in the Atlantic #OTD in 1965, Gemini VI-A astronauts Wally Schirra and Tom Stafford treated the Gemini VII crew to a festive treat: a performance of Jingle Bells with Schirra on harmonica and Stafford jingling bells.

Today marks the 60th anniversary of the first rendezvous of two crewed spacecraft in human history. The Gemini VI-A spacecraft met the Gemini VII in orbit, coming as close as one foot (30 cm) from one another. More about this milestone: https://t.co/NKLVqj3NOq

Mariner 2 flew by Venus #OTD in 1962, achieving America's first "first" in the space race with the Soviets: the first fully successful planetary flyby in human history. 📷 @NASAJPL engineers watch as Mariner 2 data is printed out on Dec. 14, 1962.

#OTD in 1972, Apollo 17 moonwalker Harrison “Jack” Schmitt became the first geologist to walk on the Moon. He and crewmate Eugene Cernan set records for the amount of time spent on the lunar surface and returned more than 240 pounds of rocks and soil.

60 years ago today, astronaut Wally Schirra kept his cool! Scheduled to launch #OTD in 1965, the Gemini VI-A launch was aborted 1 sec. after engine ignition Schirra made the split-second decision not to activate the ejection seats noting "I knew we hadn't gone anywhere." It

Look kids, Big Ben … Parliament. Gemini VII astronauts Frank Borman and Jim Lovell circled the Earth 206 times over their two-week stay in the Gemini spacecraft. In addition to completing 20 experiments, they took hundreds of photographs of Earth, including this one of the

"The Challenger has landed!" #OTD in 1972, Apollo 17, the final mission of the Apollo Program, landed on the Moon. Watch: https://t.co/65GBmsG8pc 📷 Gene Cernan with the flag, Challenger (the Lunar Module), and lunar rover during the mission's first extravehicular activity

One of the main goals of the Gemini VII mission 60 years ago, was determining the human body's response to a space flight long enough to get to the Moon and back. Frank Borman and Jim Lovell were constantly monitored. Everything they ate, drank, or excreted was noted. Their

IXPE is 4, and it’s still exploring more! #OTD in 2021 NASA’s Imaging X-ray Polarimetry Explorer (IXPE) launched on its mission to observe some of the most extreme objects in our @NASAUniverse. See what all its discovered here: https://t.co/3KnCDF9WWX

Dec 9, 1978: Four probes released from NASA's Pioneer Venus spacecraft reach Venus's thick atmosphere, collecting valuable data during descent. Two probes survive their landing on Venus's hellish surface. One sends back data for over an hour. How understanding Venus helps us

For their 2-week stay in the cramped Gemini spacecraft, the Gemini VII crew wore a lightweight suit that could be more easily removed and stowed. Jim Lovell was allowed to remove his suit 48 hours into the mission, while Frank Borman sweltered in his suit until Dec. 10.

This photo of Earth, dubbed the Blue Marble, was taken by the Apollo 17 crew #OTD in 1972 as they traveled to the Moon. It soon became one of the most widely-distributed photographs in history.

See more LRO images from the Apollo landing sites:

10 years ago this week, it was announced that the Lunar Reconnaissance Orbiter (LRO) had found the last of the impact sites for the Apollo booster rockets. After decades of uncertainty, the spot where the Apollo 16 upper stage rocket had impacted the Moon had been identified.

NASA's Galileo probe arrived at Jupiter, 30 years ago on Dec 7, 1995, becoming the first to orbit the planet. More than 6 years after the mission had been launched from space shuttle Atlantis, it was ready to get to work exploring the Jupiter system in detail! 📷 Jupiter's 4

Today we salute astronauts Jim Lovell and Frank Borman who launched into orbit for Gemini VII #OTD 60 years ago. Their mission would last for 14 days—the longest crewed space flight in U.S. history until 1973—and would be part of the first rendezvous of two crewed spacecraft.

Today we celebrate the SOHO spacecraft, launched 30 years ago on Dec 2, 1995, and the longest lived Sun-watching space mission to date!

#OTD in 1990, Astro-1 was launched on the space shuttle Columbia. It was a science platform that carried one X-ray and three UV telescopes. This pioneering mission gave us a nine-day glimpse of the high-energy universe. Read more: https://t.co/XMdBzaVDqN

Welcome to the space telescope repair shop! 🔧 To ensure Hubble's long life and continued success, engineers made sure it could be serviced by astronauts in space. #OTD in 1993, the first servicing mission launched! Find out more about SM1: https://t.co/fg1QBTMbtj

#OTD in 2018, we got an unplanned treat as NASA's InSIGHT lander let us listen to wind on Mars for the first time! The lander's air pressure sensor and seismometer captured the vibrations of Martian wind. Hear more Mars sounds recorded by Perseverance: https://t.co/EepQJCaQVR