Surveyor 3

Surveyor 3 was the third lander spacecraft deployed by the United States as part of the uncrewed Surveyor Programme to explore the lunar surface. Launched and landed in 1967, it became the second spacecraft of the programme to achieve a successful soft landing on the Moon. It was also the first lunar mission to carry a surface-soil sampling scoop, enabling direct investigation of the regolith. Surveyor 3 later gained historical significance when Apollo 12 astronauts Pete Conrad and Alan Bean visited the lander in November 1969, making it the only human visitation of a probe located on another astronomical body. Several components, including its television camera, were removed and returned to Earth for scientific analysis.

Background and Mission Objectives

The Surveyor Programme was conceived to gather critical lunar surface information required for future crewed landings. Its objectives included determining the mechanical properties of lunar soil, assessing the suitability of potential landing sites and transmitting images to support surface characterisation. Surveyor 3 inherited the general design of earlier missions but incorporated improved mechanical systems and introduced a soil-sampling scoop for the first time.
Launched on 17 April 1967, Surveyor 3 touched down on 20 April 1967 in the Mare Cognitum region of Oceanus Procellarum. The landing occurred within a small crater later named Surveyor Crater. Throughout its active period before the onset of lunar night, the lander transmitted 6,315 television images, including notable views of Earth from space, panoramic surveys of the lunar terrain and images of its mechanical digger in operation.

Landing Dynamics and Surface Operations

During its descent, the spacecraft encountered difficulties when highly reflective lunar rocks interfered with the radar altimeter. This caused the descent engines to continue firing longer than planned, resulting in a sequence of low-gravity bounces before finally settling onto the surface. Despite these anomalies, the landing met the mission requirements.
Surveyor 3’s scoop mechanism, mounted on an electrically driven extendable arm, enabled the excavation of four trenches up to several centimetres deep. Samples were deposited before the lander’s cameras to be photographed and analysed remotely. These observations assisted in assessing soil cohesion, bearing strength and surface granularity. The lander ceased operations on 3 May 1967 as the Sun set and its solar panels could no longer supply power. Unlike Surveyor 1, which briefly reactivated after lunar nights, Surveyor 3 did not resume functioning due to the extreme cold endured.

Visit by Apollo 12 Astronauts

Surveyor 3 achieved lasting prominence when the Apollo 12 mission targeted its landing site as a precision demonstration of crewed lunar landing navigation. On 19 November 1969, Pete Conrad and Alan Bean landed within walking distance of the probe and conducted extensive documentation of its condition. They removed various components, including:

• the surface-soil sampler scoop;
• structural aluminium tubes (painted and unpainted);
• segments of insulated television cable;
• and the full television camera assembly.

These items were returned to Earth for scientific study, particularly regarding their exposure to prolonged vacuum, radiation and micrometeorite impacts. The television camera, after nearly 947 days on the lunar surface, was found to be largely intact and is now displayed at the National Air and Space Museum in Washington, D.C. The sampler scoop also survived in good condition aside from minor solar-induced paint fading.

Scientific Instruments: Television Imaging System

Surveyor 3’s primary scientific instrument was its versatile television camera. It incorporated a vidicon tube system equipped with two lenses of 25 mm and 100 mm focal length, together with clear, red, green and blue optical filters. The camera assembly was mounted beneath a movable mirror capable of scanning a full 360° in azimuth and a wide range in elevation, allowing detailed mapping of the surrounding region.
Two operating modes were available:

• 200-line mode, transmitted via an omnidirectional antenna, producing one frame every 6.18 seconds with a bandwidth requirement of 12 kHz.
• 600-line mode, transmitted through a directional antenna with enhanced resolution and a bandwidth of 220 kHz.

Images were recorded on magnetic tape on Earth and displayed in real time on slow-scan monitors. Among the images were surveys of the spacecraft itself, detailed studies of trenching activity and observations of an April 1967 lunar eclipse.

Soil Mechanics Surface Sampler

The soil mechanics surface sampler performed scraping, digging and impact tests to evaluate the mechanical properties of lunar regolith. The scoop comprised a metal container with a sharpened blade and an electrically driven opening mechanism. A footpad attached to the scoop door provided added stability when interacting with the surface.
Mounted on a pantograph arm, the scoop could extend or retract, sweep through an azimuth range of approximately 40° to 72° and be elevated or lowered. Gravity-assisted drops allowed penetration tests. In total, the sampler completed seven bearing tests, four trench tests and thirteen impact tests during ten operational periods. Although telemetry limitations prevented the direct measurement of forces and motor currents, the overall mechanism performed effectively within design expectations. Penetration depths achieved in bearing tests and the trenches contributed valuable data to pre-Apollo lunar engineering models.

Apollo 12 and Interplanetary Contamination Controversy

Following the recovery of Surveyor 3 components, early analyses reported the presence of Streptococcus mitis, a bacterium commonly found in human environments. Some interpretations suggested the organism had survived dormant for more than two years on the Moon, raising concerns about interplanetary contamination and providing speculative support for panspermia theories.
The claim, however, has been critically reassessed. Investigators have noted that handling procedures, including the possibility of non-airtight sample containers and contamination in clean-room environments, likely introduced terrestrial bacteria after recovery. As a result, the episode underscored the necessity for rigorous planetary protection protocols. It influenced NASA’s adoption of strict sterilisation procedures for probes destined for environments potentially conducive to life, such as Mars or the icy moons of the outer planets. Later missions, such as Galileo and Cassini–Huygens, were deliberately deorbited into gas giants to prevent biological contamination of moons such as Europa or Enceladus.

Later Imaging by the Lunar Reconnaissance Orbiter

In 2009, the Lunar Reconnaissance Orbiter (LRO) captured high-resolution images of the Surveyor 3 landing site. These photographs revealed the lander still resting within Surveyor Crater alongside preserved Apollo 12 astronaut footpaths. The imagery provided additional geological context and confirmed the long-term preservation of human artefacts in the lunar environment.