I'm assuming you are referring to this:
http/nos.nl/artikel/202302-nieuw-soort-leven-ontdekt.html ?
The article doesn't say NASA believes the DNA to be alien per se. It only says that its composition is totally different from that of all known terrestrial DNA (as Phosporus is replaced by Arsenic in the bacterial composition. This still leaves open the possibility that the DNA originated on earth, but was formed under completely different circumstances than other life forms.
The only significance this has, is that it proves that living organisms can use different basic building blocks than just phosphorus, nitrogen, oxygen, carbon, hydrogen and sulphur. But I thought most scientists already intuitively agreed with that these.
Of course, the actual NASA broadcast might reveal totally different information, for example evidence that the DNA
must be extra-terrestrial for some reason.
Extremely minor nitpicking: NOS is a Dutch radio and TV station, so the news first appeared on TV, not in the online article.