President Trump has signed the NASA Transition Authorization Act of 2017.

The new law calls for a $19.5 billion NASA budget and asks the space agency to reach Mars by 2033.

However, the law leaves out earth science, which the Trump administration intends to cut heavily.

Update: An omnibus bill passed by Congress to fund the federal government and signed into law on March 23, 2018, would give NASA about $20.7 billion for the 2018 fiscal year.

For the first time in nearly seven years, the US government has passed a new long-term vision for NASA's future.

President Donald Trump signed the NASA Transition Authorization Act of 2017, a bill also known as S.442, into law in the Oval Office on March 21.

The Senate and House had collaborated on the document for months, and it requests a $19.5 billion-a-year budget for the space agency. (NASA received $19.3 billion in 2016, or 0.5% of the total federal budget.)

In an image that Trump tweeted on Tuesday, the president said he's "delighted to sign this bill reaffirming our national commitment to the core mission of NASA: human space exploration, space science, and technology."

However, that core mission is missing something that has been a part of the space agency since its creation: earth science.

End of an atmospheric era?

NASA Earth Observatory

The 1958 document that formed NASA called upon the new space agency to contribute to the "expansion of human knowledge of phenomena in the atmosphere".

This includes climate research, which Trump and his appointees reject despite of centuries' worth of evidence and an overwhelming scientific consensus in support of conclusions drawn from that data. (Namely, that human activity is helping warm Earth's atmosphere and accelerate changes to its climate.)

As Business Insider's Rafi Letzter has reported, NASA has carried out that mission "with gusto under six Republican administrations and five Democratic ones."

The new law doesn't even mention earth science, which troubles scientists — especially considering what the Trump administration laid out in its proposed budget for NASA, released last week.

If enacted, that budget would cut several major space agency initiatives, including the Office of Education, and seeks to terminate the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE), Orbital Carbon Observatory-3 (OCO-3), Deep Space Climate Observatory (DSCOVR), and CLARREO Pathfinder missions.

These four satellites allow scientists to monitor and predict the behavior of Earth's weather, shifting climates, ocean ecosystems, and other vital aspects of our planet. They help save peoples' lives, protect wildlife, and prepare America and other nations for long-term changes.

However, these deep cuts may or may not come to pass.

While S.442 is now a law, a long and complex budgeting process remains before NASA knows what its actual funding levels are for fiscal year 2018, which runs from October 1, 2017 through September 30, 2018.

Trump's proposed budget says NASA should receive $19.1 billion per year, or $400 million less than Congress' law calls for. Meanwhile, Trump is receiving pressure from Republican groups to acknowledge and support the science of climate change.

The new roadmap for NASA's future

An illustration of the Space Launch System taking off from Cape Canaveral, Florida. NASA's Marshall Spaceflight Center

The law asks NASA to create a plan for getting humans "near or on the surface of Mars in the 2030s."

It also calls on the space agency to continue developing the Space Launch System (SLS) — a behemoth rocket — and the Orion space capsule in order to eventually go to the moon, Mars, and beyond.

Trump has expressed support for a crewed exploration of Mars, and in his inauguration speech he said he's "ready to unlock the mysteries of space." Administration officials, meanwhile, have said they want NASA to return to the moon in the 2020s.

The American Astronomical Society has a convenient breakdown of the $19.5 billion in the bill, including funding for human space exploration, space-station operations, science, and more.

Here are some notable titles, articles, and sections of the 146-page document: