astronomy

List of Mars orbiters

List of Mars orbiters is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand List of Mars orbiters rather than just read about it. In short: The following table is a list of Mars orbiters, consisting of space probes which were launched from Earth and are currently orbiting Mars. As of August 2023, there have been 18 spacecraft missions operating in Mars' orbit, 7 of which are currently active.

Key takeaways

List of Mars orbiters belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect List of Mars orbiters to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of List of Mars orbiters from memory before moving on to harder problems.

Reference excerpt

The following table is a list of Mars orbiters, consisting of space probes which were launched from Earth and are currently orbiting Mars. As of August 2023, there have been 18 spacecraft missions operating in Mars' orbit, 7 of which are currently active.

History

20th century

The Soviets' Mars program and the United States' Mariner program became the two first successful space programs that intended to explore Mars through orbiters. Mars 2, Mars 3 and Mariner 9 were all launched into space in May 1971, and all entered Mars’ orbit that same year. NASA's Mariner 9 reached the planet's orbit first on November 14, narrowly beating the Soviet's spacecraft amid the space race, and subsequently became the first spacecraft to orbit another planet. Contact with all eight Mars orbiters launched during the 20th century has been lost. NASA's four spacecraft are conjectured to remain in Mars' orbit. Mariner 9, Viking 1 and Viking 2 are expected to lower down into the Martian atmosphere by 2022 and either burn up or crash into the planet's surface. Mars Global Surveyor is expected to crash onto the surface of the planet by 2047. The fate of the Soviet's three Mars program orbiters and Phobos 2 remains unclear, but they are still presumed to be in orbit. In 1999 the Mars Climate Orbiter impacted the Martian atmosphere.

21st century

2001 Mars Odyssey was launched April 7, 2001 on a Delta II rocket and currently holds the record for the longest-surviving continually active spacecraft in orbit around a planet other than Earth at 24 years, 10 months and 4 days. In 2003, the European Space Agency (ESA) launched their first planetary mission with Mars Express to conduct reconnaissance and exploration of Mars from orbit. On 12 August 2005, NASA launched Mars Reconnaissance Orbiter (MRO). As MRO entered orbit in 2006, it joined three other active spacecraft which were in Mars' orbit: Mars Global Surveyor (MGS), Mars Express, and 2001 Mars Odyssey; at the time, this set a record for the most operational spacecraft in the immediate vicinity of Mars. MGS has since ceased to function. On November 5, 2013, the Mars Orbiter Mission (Mangalyaan-1) was launched by the Indian Space Research Organisation (ISRO) as a "technology demonstrator" project. Its secondary goal is to analyze the Martian atmosphere and topography. The orbiter reached Mars orbit on September 24, 2014. Through this mission, ISRO became the first space agency to succeed in its first attempt at a Mars orbiter. The mission is the first successful Asian interplanetary mission. Ten days after ISRO's launch, NASA launched their seventh Mars orbiter MAVEN to study the Martian atmosphere. Its goals include determining how the planet's atmosphere and water, presumed to have once been substantial, were lost over time.

Fate

After achieving orbit, functional or not, Mars orbiters have been predicted to remain in orbit for a certain amount of time.

Viking 1 orbiter, likely to be in orbit as of 2019. Mariner 9 was expected to remain in orbit until approximately 2022, when the spacecraft was projected to enter the Martian atmosphere and either burn up or crash into the planet's surface. Mars Global Surveyor is predicted to orbit until 2046 (50 years after insertion). Besides decaying to Mars, a collision with a moon or other spacecraft is also a possibility. In March 2017, MAVEN had to change its orbit to avoid colliding with Phobos, and with an increasing number of spacecraft at Mars this risk increases. The Mars Global Surveyor is still being tracked, although it is no longer functioning.

Table of objects

Note that days active category does not necessarily equate to time in orbit, for example Mars Global Surveyor is expected remain in Mars orbit for 50 years after its arrival. The detection of derelict spacecraft in Mars orbit has some interest due to the minute risk of collision with such a spacecraft. One example of this is a proposal to use the Optical Navigation Camera on the Mars Reconnaissance Orbiter to search for small moons, dust rings, and old orbiters.

Illustrations

List of Mars orbiters: Artist's rendition of Mars Express as seen by NASA's Mars Global Surveyor — Artist's rendition of Mars Express as seen by NASA's Mars Global Surveyor

List of Mars orbiters: Image of Mars Express in orbit at Mars — Image of Mars Express in orbit at Mars

Worked examples

Example 1 — a first encounter with List of Mars orbiters

Start with the simplest possible case. Write down what List of Mars orbiters claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to List of Mars orbiters before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about List of Mars orbiters ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of List of Mars orbiters

In research: List of Mars orbiters appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses List of Mars orbiters in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: List of Mars orbiters is common in secondary-school and first-year university syllabi. It links to neighbouring topics Lists of space probes, Mars orbiters, Missions to Mars, so understanding it makes those chapters shorter.
In everyday life: Look for List of Mars orbiters outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study List of Mars orbiters in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what List of Mars orbiters means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain List of Mars orbiters out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is List of Mars orbiters in simple terms?

Why does List of Mars orbiters matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study List of Mars orbiters?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on List of Mars orbiters.